a little help?

Took another at 2 just to check and the line was a little darker but still negative. Took another @ 5pm it was just a shade lighter than control line. So me and my so dtd. I took another before going to bed at 9:30 and it was almost a positive but not darker than control... so this morning (cd14) I took another opk @4am it was positive darker than the control line. I took another one when I got home from work at 5 (held my bladder for 3 hours) and it was negative. So we Dtd again. Took another one at 8pm negative... so my question is, is it normal to have an lh surge that short?since I had a negative opk this evening, does that mean that I possibly ovulated today?  I had a little twinge and slight cramping on my left side today that lasted about 2 minutes.