You are suffering from irregular period & TTC for last 7 months.
There are several reasons like hormonal
,wt gain/loss,emotional upset,ovarian cyst
,irregular eating habit etc.
Do some investigation like USG lower abdomen,LH/FSH,thyroid profile etc to rule out underlying pathology.Then consult with gynecologist and take T/t accordingly.
Pink spotting after intercourse may indicate previous implanted bleeding and have to confirm by USG.
Do intercourse around ovulation time by using OPK or other methods.
Avoid stress,control body wt,take healthy diet and need proper sleep with Vit-E supplements.