Please help me - don't know what's going on!

I've been having some abdominal pains for about 2 years now. It is very sporadic and I can go months without it bothering me. However, it can be so painful that it causes my eyes to well up with tears (this hasn't happened often though). The doctor took blood tests and everything came back normal.

Recently, I have been feeling constipated but it's really watery and when I'm done on the toilet it feels as if I still need to go.

Does anyone have any idea as to what's wrong?
I would be very grateful for any responses.