pain in lower right abdomin

Hi all

I'm about 21 months out from surgery.  The pain started yesterday around 5 pm. I could only eat 1/2 my supper.  I was uncomfortable most of evening.  After I went to bed,  I did get to sleep but about 1:30 am, was very painful, I thought maybe was having either a gallbladder attack or my appendix I looking up symptoms and all I had was the pain.  Is on right side half was down my abdomin to my groin.  I also thought might be bowel abstraction as I didn't go Monday or Tuesday,  but small amount yesterday.  

I made it thru night. And I did have good bowel movers u took it that maybe that was pain,  got little better but pain still that, not as bad, but hurts more when I try stand straight up.  

I also have pretty bad headache.  If not getting better by tomorrow will go hospital where I had my surgery.  

Thanks 

Cathy