I am Muslim and i saw something online about prophet Muhammad that made me upset so i started researching about his life and his wives online. I had some negative feelings toward him but I quickly stopped. I feel guilty, does this make me a disbeliever now?
Bismillahi Ar-Rahmaan Ar-Raheem
If you did not affirm it, or believe in it, then you are not a disbeliever. Do not be swayed by the tricks of Shayateen among men and jinn. You can be sure 100% of such claims are (as you will see In Sha Allah) laughable. However, you should do your best to resolve doubts as soon as possible. Here is a useful resource for solving common doubts.