your left sided follicle is getting small day by day indicates ovulation arround 12th day . If you had sex arround 11th to 13th day this time there is chance of conception.
is a conditon of harmonal imbalance,bringing about ovulatory problems .but don't worry- there are medicines/surgery to correct it.
pl. consult a good Gynac -for investigations &t/t.
wish you al the best!