Cheating?

Me and my bf have been together for about 9 months he’s a good bf but yesterday i saw he had messaged a girl and i told him to open the message and he had commented “😍😍😍” on a picture she posted of herself it really hurt to see that he says he doesn’t remember sending it but he know he did do it (obviously) i feel like that was cheating am i wrong to be very upset or should i just ignore it and keep going i told him how i felt about it he’s apologized but I’ve been cheated on in the past i just don’t know what to do