Trying could someone help me figure this out

So me and my boyfriend have been trying for about 4 months and I just started taking prenatals at the end of last month cause the doctor said it could help if I want to get pregnant so I’ve been taking them this month none stop and I feel like I had implantation bleeding on the 15 I had it and the it stopped that day and then o had it on the 16th and then it did the same thing then it skipped on the 17th and the I had it again on the 20th and it stopped all in one day I didn’t even have to where a pad or pantyliner on those days and I was supposed to start my period on the 24-26 and it hasn’t shown up I’ve taken a few test they said negative maybe it’s to early or idk maybe I should wait a month or go see my doctor