Pain on my right side

The last few weeks I have been having some pain on my right side where my ovary would be. It's not debilitating but more of like a dull ache I guess. I'm on NuvaRing and have been since April. Last month my period was very light and very short. I have gained like 4lbs in the last 2-3 weeks and it all seems to be in my belly area. I took a pregnancy test about 2 weeks ago which was negative but I'm not due for my period until the beginning of October. Curious what others think if anyone else has had this.