Period troubles

I’m reaching out to hopefully get some advise or answers... the past few months my period has been a mess. Iv always been regular but lately it’s been all over the place... never on time.

This last go round has taken cake... I am 18 days late, still having period like symptoms like light cramping and about a week ago my nipples have been super sensitive and tender. Iv taken a pregnancy test a few days ago just to rule it out and it’s negative. Iv also recently had blood work done just to see if anything weird is going on there and things came back fine.

Things just don’t feel right and I have no idea what’s going on. Has anyone else dealt with this before?