My 7 year old daughter just started singulair 3 nights ago. She t...

My 7 year old daughter just started singulair 3 nights ago. She took her first dose on wednesday night and thursday morning she started with bad stomach pains. later that day she went to the bathroom ( #2 ) alot and cried in pain when she went. We thought it was a stomach virus but after reading all of this I think it might be the singulair. That is the only symptom. Stomach pain and pain when going #2. Has any one else gone through this also??? I just gave her a pill a hour ago and decided to get on the internet to see if it might be the singulair. Now I feel bad for giving her that last dose. Does anyone know how long it takes to go through the system and how long till her pain goes away???