What’s wrong? I’m still nauseous and still pee a lot and my boobs and back hurt

Hello my name is Rebecka.

Ok so I and this guy I’m dating had unprotected sex on 10/13 witch was the day I was most fertile. I did not know that tell a couple of days later. I already have a kid and well I got pregnant the last time I had unprotected sex on the day I was most fertile so I’m freaking out. So I was supposed to start my period on 10/24 but I didn’t start tell 10/28. The week before I started I was really nauseous, loss of appetite which is never like that when I start I’m always really hungry the whole period my breast are kind of tender but I barely notice them at all I’m constantly constipated and I keep getting really bad headaches and I’ve been using the bathroom so much lately, I also took a pregnancy test on the 10/26 but it was negative. Idk I think it was too early to tell if I was pregnant....but I started my period and when I did start it was super light not even like a period the first day and a half then it got a little heavier and now it’s like a normal period but I don’t understand what’s wrong I’m still nauseous and still pee a lot and my boobs and back hurt and I get random headaches I just feel like complete sh*t. You would think I would know if I was pregnant or at least remember what it was sense I’ve already had a kid or I would at least remember what it feels like but this seems so different then the last time if I am. I need some advice please help could I be pregnant or am I just freaking myself out?