implantation bleeding?

Okay, I had unprotected (he didn't pull out either) sex on 6/10, 6/11, 6/14, 6/15, 6/18. On 6/18 I had light brown discharge, but only twice that day. Today (6/22) I have cramps after sex. I'm also 5 and a half months postpartum and haven't started my period yet. So Idk if it was implantation bleeding or my period is about to start, but it has been 7 days since the brown discharge and no period yet. Idk if I would get a + this early on so I haven't bought any tests yet. Please, any advice helps!!