Sex and crying

So I am dating this guy and I love him like so much I have honestly never felt like this about anyone and he makes me so so happy... we have sex often sometimes like 2-3 times a day, I took his virginity and I feel like our sex life is really good. We both always do whatever we can to please the other person and we both always finish... and it’s great blah blah. Anyway sometimes when we are having sex I get that like rock in your throat feeling and like I’m about to start crying idk why.. but I get overwhelmed with this like incredible sadness.. I have never had a bad sexual encounter and I just don’t know why I feel this way... I usually just kinda push him off and say he’s hurting me but then after words I feel so terrible about it. Can anyone relate or have any advice??