My bf has just opened up to me that he had in January with another girl but still pretends to luv me?

i've bn going out with my boyfriend now for 3 years without though he do ask for that at times but i have not accepted doing that with him. He later on told me that he had in january with another girl friend and she do visit him at times but he still pretends to love me. I've bn confused and wounded in heart since he revealed this to me though i did not tell him anything, i just cried. should i leave him or what do i do.