Should i just forget him or get answers ! still so shocked?

i dated a guy for 2 mths and we had such great chemistry etc and started to fall for each other well i did now im not so sure about him. but the talks we had were great i met some family and spemt time with them then i get a call from his phone but it want him it was a female telling me shes his girlfriend for 4 yrs i was so dumbfounded because we had talked the night before and hung up the phone fine. i blasted his text with a message when i found out hes been silent since and even as i demand some explanation or an apology he says nothing. but the feeling that i deserve even the respect of an explanation and unanswered questions is killing me! should i feel like like this should i just forget about it ? how can people do crap like that !