What’s going on with my boyfriend?

I had a ex where if we had sex everything went normal and he was hard the whole time and during it. But now my new boyfriend of 1 1/2 year when we tried to have sex his dick was hard but once it touched my vagina it went soft. He doesn’t go soft for head or anything like that only when we try and have sex. I don’t know what’s going on. Someone please tell me.