did protected sex cause very low bleeding?

Hi,
Welcome to ehealthforum,
Regular menstrual cycles indicate that you are having regular and periodic ovulation (egg release from ovaries). Intercourse (especially during your fertile days) can lead to pregnancy. The symptoms of lighter bleeding and changed period pattern along with weight gain could be suggestive of possibility of pregnancy. Look out for development of any other new symptoms if pregnancy is suspected. Wait and watch for your periods. If you do not get your periods within 10 days of expected period dates, or if you get abnormal periods, or if you develop any new symptoms, or if you suspect chances of pregnancy, you should consider visiting your doctor/gynecologist for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately).
If pregnancy gets ruled out, further evaluation would be started to look for the underlying cause (hormonal derangements, thyroid hormone abnormalities, ovarian cysts, PCOD, etc) for the changed period pattern. Get started on appropriate treatment as indicated by examination findings and investigations results to help you regulate your periods. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any unusual/new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.

dear Dr madhumita
thanks for d reply
sorry i forgot to mention that i used to gym i quit a year ago, due to no proper exercising i gained weight,had intercourse on oct 6th,got my periods on 19th of the same month,should i suspect for a pregnancy....????
thanks
regards
myth