Confused

Okay so I’m fairly new to the whole sex thing so I’m sorry if this sounds dumb but my boyfriend and I have been having sex for over a month now and we have always used condoms. However I noticed after we’re done using it that he’d have this thick white substance on the outside of his condom. Is it possible that the cum could have leaked from the top of the condom to the outside or could that just be my discharge that got on him. I’m asking because I’m 3 days late on my period and I’m kinda freaking out. I took a pregnancy test two days ago and it came out negative and I’ve been showing symptoms of my period (if having tender and sensitive breast really is a symptom of an upcoming period) but none of that has helped ease my mind. This happened last month when I had sex for the first time and I was over a week late on my period but I thought that would just a one time thing but it seems to be happening again. If anyone went through the same thing and can help give me some peace of mind that would be amazing 😂 Idk if I’m just being overly worried or if it might be an actual cause of concern. Let me know what you guys think!