Is there something wrong with me?

I've been with my boyfriend for 3 years now. We had a decent sex life but then life happens and my mental health got in the way. Long story short, my sex drive is barely existent now due to antidepressants. Last I remember we had sex maybe less than a month ago. My boyfriend has been so amazing and understanding. He's helped me through so much and I'm so grateful for everything.
Anyway, tonight we started making out and then next thing you know sexy time commences. Everything was great until midway through having sex I burst into tears. To the point where we had to stop completely. I was so embarrassed! I was apologizing profusely and making sure he was okay with us stopping. I feel like I'm going crazy because I can't stop thinking about how horrible I feel for ruining our moment. 
I honestly don't know what will come of this post or why I'm writing it but I thought I'd share and see what you guys think. Any advice or possible thoughts of why this may have happened are welcomed. Thanks.