I feel a slight fluttering on my lower left side, pregnancy test all negative, please advise?

I am 52 years old and stop having my period a year ago. But for the last 2 weeks I’ve felt that butterfly feeling you get when you first feel a baby kick. If I look hard enough I can sometimes see a jump in my stomach Its off and on most days especially at night. I’ve had 2 children and swear it feels exactly the same. I’ve taken 3 home pregnancy test and all were negative. The slight fluttering is on my lower left side just above the bikini line and below the belly button. What could this be? I’m also on Adderal and I saw online that can cause false negative results. Also about 2 months ago I did have some slight bloody discharge for a few days but not a real period. Went to a clinic to be check for Std. Which was negative.

Age: 52
Female
Medications: Adderal