Ovulation confusion

Hi everyone,

I'm so confused right now and hoping I'm not having any major issues. I began taking ovulation test (the little strips) on the 12th day of my cycle so that I could be absolutely sure of when I would start ovulation. They were all negative. I got what seemed like a positive ( test line was definitely darker than control line) on the 15th day. On the 16th I took three more test in the afternoon and the test lines were even more prominent than the control lines so I was sure that the 16th was the day. I didn't do any test on the 17th and 18th day of my cycle but on last night (18th) I started having really sharp pains on my lower left side. I'm still having the pains so I took three more ovulation test and all three are positive just like on the 16th. I don't know what's going on with my body. Is this normal or has anyone else experienced this type of ovulation?