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Since your periods were irregular, it is difficult to comment on the probable conception date and gestational age. If pregnancy has been confirmed, go ahead with getting serial HCG levels estimated. Doubling up of the hormone levels in 48-72 hours will show that pregnancy is going on smoothly. If levels are not adequate, then external hormonal supplements would be considered to be started to help you in preventing miscarriage/threatened abortion. A transvaginal scan done at 6-8 weeks of gestation will also help to confirm fetal heartbeat, gestational age of fetus/baby along with fetal viability (early scans can fail to detect fetal pole/heartbeat). You can consider getting the scan repeated after 10-14 days. Visit your doctor/gynecologist for further evaluation and assistance. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet.
Take care.