Need some advice please


So after having my LO who is now 4 months old things have been very different with my body, after having my 20 month old I went onto the pill and my periods was normal 4 days Mother Nature called, 28 day cycle, my body was fine even after a hard labour but this time I have been on the pill for 3 months now and the first 2 month my periods was normal nothing to complain about, but this month my period started on the 4th august and I haven’t had a break at all, my stomach is bloated, and I have real bad pain in my stomach, I am loosing weight and it’s not from eating, I feel nauseas and have headaches a lot please someone tell me if there is something my doctors are neglecting as I have told them and they are saying everything is fine but I know my body and it really isn’t :(