Has your baby ever had this?

I am feeding my 12 week old baby boy and he seems to be ping is bowels regularly and they they look regular (he doesn't seem to be constipated). However, he really struggles to go to the bathroom and often squirms and cries (sometime hysterically) when he can't get it out right away. Sometimes when he is eating he starts to poop and will cry and not eat until it pes. I told the Doc about this at his last visit and he said that he will grow out of it he is just learning how to use the bathroom, but it seems to be getting worse. I also noticed a red ring around his area when I change him and it is not a diaper rash. Is this normal? Has any one experienced this with their baby and what did you do to help it out. I feel really bad that he is suffering and I don't know what to do