Worried

Ladies please help I have been trying to Gain weight but I'm struggling, I even took Bco, B12 injection and went for pills also but still no like and then i got a Iron problem taking pills and now I have stopped cause I'm suffering when I'm doing number two I'm so worried I'm daughter is 1 year and 4 months now did even gain that much when I was pregnant now from that time I'm not gain at all instead I'm losing weight more I'm so worried I don't know what to use anymore to help me gain, getting stressed and thinking too much can that be an infect in my struggling to gain?