"Stretching" Pain - Question

Karrotelle

So last night I was asleep and woke up around midnight to the most intense "stretching" pain in what I imagine is my uterus. Basically it was directly below my belly button, above my vag. I was actually in so much pain I woke DH up because I was whimpering and he was ready to take me to the hospital. I decided to go pee and have a glass of water  first and see how I felt and within 10 minutes of peeing, I felt fine, the pain was gone and I was able to go back to sleep. About 4 hours later, I woke up again with the same pain, realized I REALLY had to pee, went pee and instantly felt better.

It seems as though the minute my bladder is full, I get this pain. I'm still so early in my pregnancy. I just hit 4 weeks today and so I really don't know if it's just my body reacting to the changes or what.

Has anyone else experienced this? Do you think I should be concerned?