Situation between me n my ex's mother?

Well i broke up with my 3.5 years ld bf. nearly 9 months ago... But i'm still in contact with his family especially with his mother and he knows about that...i met with his father and mother before and they really liked me and they didn't want to lose connection with me and since we broke up she called me and still she does...I dont know what to do...this situation is disturbing me as i dont want him to think that i still contact with his mum bcause i still want to get back with him...but she is very sweet person and i really dont want to hurt her...she likes to talk to me abt anything! last week while i was talkin with his mum on msn he saw her talkin to me ! and her mum asked him if he want to say hi to me !! which is pissed me off ! and he just left room without saying anythin! Dont know what to do, should i stop talkin to her ?