Having pain and redness in right hand thumb with slight swelling. similar pain started during pregnancy. now i hav 8 month old son. pain has reappear?

Hand swelling: One of the conditions that can produce recurrent finger/thumb swelling, redness and pain is a recurrent infection and typically a paronychia. While this is not specifically related to pregnanacy, it is one condition that can recurr sometime later. Other than that, i'd say an exam would likely help a lot. Regaradless, given the recurrence and that you have an 8 month old, i'd get it checked out.

Tendonitis: This could be a form of tendonitis called dequervains tendonitis. Look for a hand surgeon and schedule a consultation in your area.