menstruation after manganak..

4months na since nanganak ako mga momshies..nungg 45days ko nagtake ako ng daphne pills mix feeding ako sa baby ko..after takin 8 tablets sa pills ko nagkamens ako not exactly sure if it was menstruation ..so i stop taking the pills .and start another pack.after taking the first line of the pills i had menstruation again..so i decided to stop taking daphne pills ..now my baby is already 4months at never pa ako nagmemens..im worried na baka mabuntis ako..nag pt ako kanina negative naman..so ano kaya nbakit dina ako nagmens? any idea mga momshies..