Semen upsetting my tummy?????

I am wondering if anybody else gets a tummy ache after swallowing semen? I've been involved in a small group sex thing with 4 to 9 guys for a few years now and I notice that if I swallow multiple loads of cum I will get a tummy ache. If it's just me and my guy I never have that problem and typically don't have the problem if it's just me and maybe 2 other guys. Everybody in the group is healthy and disease free. 9 of us got together yesterday and over a 2 hour period I swallowed Each of their loads and each of them came 2 or 3 times so I swallowed a total of 22 loads. I had a tummy ache for a while after that. Is it just the quantity of cum that I swallowed or could it be that some of the guys cum does not mix well with the other guys cum?