The chances of pregnancy are almost nil because even if he ejaculated, the egg is formed after 10 to 12 days of starting of periods. So, in absence of egg , pregnancy is highly unlikely unless you are extremely unlucky. So, my best wishes. Just relax.
You can do beta hcg blood test. If its negative then get your thyroid profile, cbc, blood sugar fasting checked from some lab.If everything is normal then do an ultrasound of abdomen.For more details you can consult me.
If last period was 26/10 then 5 weeks pregnancy at this stage is unlikely. Check dates again.
Drugs for termination of pregnancy can be taken only under the supervision of doctors licensed for termination, so meet Gynecologist.
Since you are having irregular cycles infact prolonged cycles unwanted 72 may will further delay cycles also if that happens do perform an early morning infact first urine sample urine pregnancy test at home whenever.