Irregular periods. And what should i do?

Dr. I have a issue of irregular periods and i am suffering from this since more than 2 years, sometimes i got within 28 to 32 days, and sometimes i have to skip 1 to 2 months. I am sexually active also. This time i have intimate with my partner in 22nd feb without any precaution but there was no ejaculation in my body. Moreover i got periods after 2 weeks i.e. 7th March. But after that 2 months already passed and i am not getting periods. I am very nervous from the thought of pregnancy. Even i have done 2 pregnancy test with gap of 1 week between them, both have showed negative result that time. I have kept that used 1 kit for five days and it shows second line also, very light. Now, i am in dilemma whether is there any chances of getting pregnant because i don't want too. Also from April my schedule has been totally changed like i have been working in night and taking sleep from 5 am to 11 am. And why my periods is not happening. Is there any problem and what should i do?