Cramping and discharge

I had my 3rd daughter 👶🏼 10wks ago and she is exclusively breastfed 🤱🏼 For about two weeks now I’ve had slight cramping and a few days ago I had a little brownish discharge for a day. I didn’t have my postpartum appointment because my doctor canceled it and I never called back to reschedule. My husband and I tried to have sex once a few weeks ago but we didn’t get a chance to finish because of the other kids interrupting lol.

Any ideas what could be causing this? Should I go to the doctor?