I get sickly after I have sex.. options on it would be nice

So I'm a little nervous on this.. So for about a month and a half I have been getting sick and sickly feeling after I have sex.. I would like some opinion on this.. if y'all have had are know of someone who had a situation like this.. so I don't know if it's from my neck problems. Cause around the time it started I was going to physical therapy for my neck... And I figured that maybe my muscle or tendon that is mess up is getting paint and it's making me feel like I'm getting sick.. well no feeling there I do get sick.. I have done went and had blood work done cause I thought maybe I was pregnant with a period.. but it turned out negative so I'm completely lost in why it would be happing.. I don't know to be honest.. not sure which group to post this in..