Implantation cramps?

So I am not sure when I ovulated this month. I am on thyroid medication and my dosage changed and I think it tampered with my cycle. My hubby and I have had sex almost every other night since my period until after I was supposed ovulate. I either ovulated on the May 25th or May 31st. Last night I had some twinges/slight cramping on one side of my abdomen that went away after 20-30 min. Today randomly in the store I started cramping, but it doesn’t feel like typical cramps. More like a tightness. That went on for a couple hours. I’m not due for AF for another 7 days. What do y’all think - implantation cramps?? What do these normally feel like, and when should I test? This morning’s test was negative.