I Am 19 Years Old I Always Had A Regular

I am 19 years old I always had a regular period I got pregnant in 2015 and gave birth to a baby boy. We're still irregular after that but I always get it at least every other month this year I miss my period for a little over six months I believe so it's been about 6 months since I've had it today I started bleeding it's very very light like a light pink what could cause this can this finally be my period Or is it something else I took pregnancy test they all came out negative. Me and my fiance are trying to conceive again and it's very frustrating when I have irregular periods