Foreskin doesn't retract, then it does then it doesn't do it now?

Does your foreskin get swollen around the opening when your try to pull it back when flacid or erect, how far can you normally pull it back in either state and have you ever tried stretching exercises to stretch the opening of your dose skin?

It may of just been that the head of your penis was more lubricated that time when it happened and did it slip back over the head easy again after pulling it back?

i can just pull the foreskin back a tiny bit, and maybe see the top of the penis head. nothing else. and yes it does get swollen and no i haven't done stretching.

I would suggest that you try the stretching exercises, get some baby oil to massage into the foreskin to keep it soft and help with the stretching and to use an ice pack on the foreskin if it gets swollen
Do you know how to do foreskin stretching exercises?

i have no clue

The best time to do them is when you take a bath so the foreskin has time to soak and soften up or if you don't take baths just use a cup of warm waster an let your penis soak in it for about 10 minutes, you can do the exercises either when erect or soft normally erect is better, start by gripping your penis about quarter the way down the shaft and gently pull back to retract the foreskin a little, as you feel it start to get tight just before it causes to much discomfort stop and hold it there for a minute then repeat around 10 times, if your foreskin gets swollen put the ice pack on it for 5 minutes and it should help reduce the swelling, repeat this process twice a day mornings an night's also massaging the baby oil in before and after tries, after about a month you should notice some improvement on how far you can pull it back, one thing to not do is to try to force It back to quickly as you can cause scar tissue to form making it harder to stretch
If you have any questions feel free to ask, also if you make yourself a free account on here you can private message me after you make 3 page posts on your account that way I'll be sure to see you questions.

Any good substitutes for baby oil if I don’t have any? Moisturiser?

Not really as a lot of those may irritate the sensitive skin on the glands of the penis if it happens to get inside the foreskin where as baby oil is specially for delicate skin, also with baby oil if it does get under the foreskin it will help soften any smegma that's accumulated under there.
You can pick it up in most general stores easy and its also a good lubricant for masturbating with.