Pregnant on IUD with ex-boyfriend/friend's ex-boyfriend?

Hey all, I know the "Am I Pregnant?" questions on here can get a little annoying sometimes, but I am trying to make myself a little less anxious before I go buy a test and would really appreciate some help (also I apologize for the long post, but this whole situation is just...I'm going nuts right now).

So August of 2017 I got the Skyla IUD and was off to a rocky start with my period regularity but after a few months it evened itself out and I've had pretty consistent cycles each month. Last month, though, my period came about 4 days early and lasted a little longer than usual. I'm currently away at college (just turned 21) and an old flame of mine came to visit and we ended up having sex, without a condom. I was still on my period at this point, and it lasted a couple days after he left. 

Now this is where it gets crazy. 

This story could be a damn novel if it has a happy ending. The first reason why I'm so completely horrified by this situation is the guy who is involved. He's not a bad person, he's actually really great. I love him to death. But after we broke up a couple years ago, he ended up meeting my (at the time) best friend and they eventually got engaged and she became pregnant. What makes it worse, is they broke off their engagement and he ended up finding out that the baby isn't his.

So it's like a weird swap thing going on with the three of us and I'm just in awe that I put myself in this situation.

The second reason is that I'm 21 and in college and terrified to have children, obviously. I've literally held a baby once in my life, and I almost dropped it. It was horrifying.

Now, to the hard evidence. 

I started myself on the Gardisil shot (just got the second shot of three) since I didn't get it when I was younger and so I've seen my doctor during this time and had to talk to her about this weird thing that happened. I got a new shirt at a festival that I went to and wore it a couple days later and my nipples hurt so bad while wearing it. I ended up chaffing them and maybe two weeks later I squeezed this weird sticky white fluid out of one of my nipples (just one!). I was told that was normal from the chaffing and just leave it alone.

Flash forward to today, I am 3 days late and driving myself insane with nervousness. I'm home for the summer working, and have been doing a little bit more physical labor than usual out in the sun, so I'm decently sunburned as well. So now, I'm late on my period, my muscles ache so bad, and I'm burning up for some reason and sweating like crazy (I think because of my sunburn). Then today after mowing my lawn and weed wacking, I get inside, sweaty and sore, and curiously look at my nipples and squeeze the one and there it is again, and it's still just the one, not the other.

At this point, even if I am pregnant, there is no way that I'm lactating because I would only be (God forbid) 4 weeks (exactly). 

Last night I went to see the guy and wanted to talk to him about it, because we've been talking more and there's a possibility of us getting back together and I feel like this is something we need to discuss. When we dated, he made it clear that he wants kids and whatnot in the future, and at the time, I didn't want them (part of the reason we broke up; although I do want them now just not right now). But I chickened out because I wanted to wait and see what happens and also because of that immensely awkward and complicated history we have. And I don't want to say anything to him because I don't know how he's going to react. What if he's angry or upset or happy? What if he's heartbroken if I end up getting my period? And I know he'll be stupid and ask me to marry him (super old-fashioned that way), and I'll say no because I don't want to get married because he thinks that he has to. But if I am pregnant then I'm going to tell my friend (his ex) because we are still close. And my parents don't even know that I still talk to him...actually no one does, we've been keeping it quiet. This is bad!

I'm driving myself nuts! I have actually planned out so many different situations in my head. 

Writing it all out, I feel a little less worried (and a little more crazy), because I'm assuring myself that I'm fine, but there's still that teeny tiny voice in the back of my head telling me how much my vagina is going to hurt in 8 months.

I just need some feedback on if you think this is an actual concern I should be having. I got on the IUD because of a hormone imbalance, my cycles were all over the place and awful mood swings, and I got Skyla specifically because my doctor said that I would still have a period each month, but everytime I have sex and I'm even slightly late I get incredibly anxious that I could be pregnant, even though I'm on birth control.

Thanks for reading all the way if you got to this point.