TMI but need some input!

So just the last few hours I've been having a sharp pain in my lower abdomen ONLY when trying to make a bowel movement (been constipated today) and I'm wondering. If anyone else ha experienced this?? It goes away immediately after I stop trying to 'push' as it were.. And I am about 5 weeks pregnant (just found out on Saturday) my doctors appointment isn't til next week. I think if it keeps up I'll call my doctor and ask tomorrow if it's anything to worry about but wanted to see if anyone has experienced the same thing! Thanks in advance!