What Are The Side Effects Of Advil?

I have a vein tht the doctors looked at 2 years ago ran x-rays and checked for blood clogs and checked my hurt. I'm having the same problem again. The test came back good. What is going on with this leg, they gave me some advil thats helps but what is really going on. Sometimes it hurts when I walk and after I have been laying down and get up it hurts realy bad.