Cramps during intercourse

Husband and I had intercoruse. It's stupid to say but we did it from behind. And at the begining I felt cramps in lower stomach. And when I tried to stand up cramps were so strong that I couldn't do it. It was painful and lasted few minutes and it goes away. We continued and everything was fine, there was no bleeding or anything after. Is it normal? Did it happens to anybody?

Was everything ok with the baby?

I'm really worried so please help. My next app is for a month so I don't know what to do till then