About 3 weeks ago my boyfriend was grinding on me, we were both fully clothed

It is highly unlikely you would get pregnant from what little you have said.

1. What exactly did you mean by he "touched me over my clothes"? It is highly unlikely that sperm could swim through the fabric of leggings and a thong unless both were extremely thin/open-weave and you (and the fabric) were very, very wet. Even so, sperm would have to find its way to your vaginal entrance and then enter.
2. What other sexual activity have you had (and when) since your previous period?
3. Was your period that "was just spotting for a couple days" unique, or have you had times like this previously?
4. What were the dates of your last 3 period starts?
5. What is your usual cycle length (typically 28 days)?
6. How did you ascertain that it happened in your fertile window?
7. How old are you?
8. Where are you from?
9. Are there any cultural/religious implications?

I hope this is a help as a start, but I wait to hear back from you to see if I can further allay your fears.

Thank you for responding.
What I meant from touching over my clothes is he was rubbing me over my pants over my vaginal area.

My thong was cotton and my leggings were spandex. I don't believe they were open weave but I was wet from my own discharge.

I have not had any other sexual contact. Only this which was approximately 3 weeks ago.

I did have some blood clotting today so I am not sure if my period was just delayed.

I took a home pregnancy test and it came out negative but my breast feel tingly and heavier than normal and I have been sick to my stomach for the past couple days.

My period is typically 24 days.

I believe it was in my fertile window bc it was 12 days before my next period.

I am in my early 20s and don't have much sexual experience due to strict religious beliefs.

I am so very very scared that I could be pregnant.
I learned a very valuable lesson I just hope it's not to late. Would a pregnancy test show positive by now?

12 days before a period is due is not likely to be a fertile time. From the detail you have given, it is highly unlikely, if not impossible, that sperm could have got to your vagina.
You haven't given an exact date when this happened, but if it were 19th Oct or before, then a test would certainly be reliable now, and likely to be reliable anyway. I don't think there is any chance of pregnancy.
You say that you have learned a valuable lesson, which is good. Have you considered how you will make sure you don't get into this state again?
I hope this helps.

From what I have read and I have read alot (probably too much).....i thought 2 weeks after the start of your period is your fertile time. The exact date this happened was October 21st and my last period was October 11th and than again the spotting on November 3rd.
I was in Urgent Care on Friday, November 4th due to my Kidney stones and because they did a CAT scan on me they had to do a blood pregnancy test which came out

The test came out

If you have a regular typical 28-day cycle, then 2 weeks after your period starts would probably be the day you ovulate - Cycle Day 15 (CD15). However, as sperm can live in a woman's body for up to 6 days, then the previous 5 days are also considered to be fertile days (CD 10-15).
However ovulation is not really directly linked to your last period, but rather your next period is linked to your ovulation. A period usually starts 2 weeks after ovulation (assuming no pregnancy) when the womb's preparation for pregnancy is no longer required and is discharged in what we term a period.
This means that if the cycle is 30 days, then ovulation would occur CD 17, and fertile days would be CD12-17. Likewise if your cycle is 24 days, then ovulation would occur CD 11, and fertile days would be CD6-11
With a 24-day cycle and a period starting 11 Oct, 21 Oct could have been your Ovulation Day, but as you had spotting on 3 Nov, it is likely you ovulated a day early, so 21 Oct might not have been a fertile day. Anyway, the blood test on 4th Nov would have picked up a pregnancy. So you are not likely to be pregnant.
I hope this helps.

So blood tests are very reliable?? Thank you for explaining that to me. I do use and app for period tracking but not for fear of pregnancy like I feel now but just to track my cycles.
You seem very knowledgeable about this. Have you ever heard of someone getting pregnant threw clothing. The internet can be a scary place.

Blood tests are reliable, and can detect pregnancy earlier than home tests.

There are those who claim to have got pregnant that way, but I know of no verifiable incidents (nor have I done extensive research).

Remember that sperm swim - they cannot walk or crawl. So to pass through clothing there would have to be a lot of fluid and room for them to swim through the fabric. Then there would have to be enough arousal fluid for them to swim into the vagina.

I would think that there would have to a full ejaculation onto open-weave underwear (like lace) right at the entrance of a very wet vagina for there to be any realistic chance of pregnancy following. But it only takes one sperm to survive the hostile journey!

I hope this helps.