Late period negative test werid things happening any help or advice please would be greatful ?

With my body personally sometimes i wont a get a period for like 2-4months at a time, i get extremely worried as im in a relationship to also with no cheating or diseases, and we are careful. i took a test last week and it was negative 2month since my last period but when this happens i do get a brownie discharge then after a few days gets redder and redder till im fully on. i get cramps and twitches in my tummy. i have had these odd periods a lot where i think im pregnant (even though im careful and nothing has split or anything) i can have a 6 month regular period where it is fine then BAM that happens im not sure what is happening in my body but i have never been pregnnt so i wouldnt worry to much if i was you and maybe if nothing is happen in a couple weeks then take another test.