HELP!?!?!!

Ok this is might be long. Basically I was in a relationship with someone for 3 years and we broke up in November for no real reason just the fact college is getting crazy, we both just got weekend jobs and we live far also the spark just kinda wasn't there. Anyway it was a nice break up we agreed to be bffs still as we are very special to eachother but I thought I needed some time apart and so blocked him on everything for a few months. On Christmas we spoke again and started following each other back. We had some argued in this time but still spoke at times. We agreed to meet up for a coffee one day and then he would come to mine for dinner as I had move house and we wanted to come see it but also my family love him. Anyway it was great and we were able to catch up n stuff but I could kinda tell when he was leaving that he started to miss me again. Anyway a few weeks after he was meant to come round again but this time he initiated the idea of having a sleepover and (ofc) we had sex, but we spoke about everything it wasn't just that. We did it twice; the first time was only for 20 minutes and we didn't use a condom, the second time we didn't use a condom for like 10 mins but then put one on and since breaking up I removed the implant and so am not on any form of birth control) This was on a Saturday, the following Thursday I was meant to get my period and I didn't which I was a little like 'hm ok this shouldn't really happen but whatever' anyway I completely forgot about not having my period until like 1 week later when I remembered and was like shit, so I told him and he was a bit like wtf but I told him I had a test at home and was gonna take it. So I did and it came back negative, I felt a lot better but it's now been 3 weeks and I still haven't had my period. Also my nipples are extremely sore. Can someone please help me, I haven't been freaking out (which ik some people would say that's probably why my period won't come, but I'm really not)