It could be for a number of reasons:

It could be that he wants to see what's happening down there during your intercourse. That can be very sexy for a man. (Don't forget, typically, a mans sexually can be very visual.)

It could also be because he wants to have more control over his 'sexual technique'. In other words, he wants to make sure his 'aim' in spot on to make sure he's giving you as much pleasure as he can.

Another reason is that he may be doing it because it feels natural for him to do it. A lot of the things we do during sex can be natural responses to the passion you are sharing.

I wouldn't worry too much about this (as your post says, it doesn't really bother you). But you should be able to talk to you boyfriend about these things. If you are ready to have sex with him, you should be ready to talk to him about anything!

However, if you are going to talk to him about it, make sure he knows that doing this doesn't bother you. He may worry that your uncomfortable with it.

Hi,

thanks for the response

no i think this is a new thing for him we have been together for a year and a half now and hes just started doing it!

I dont mean i feel uncomfortable speaking with him about it i just dont feel its something i need to ask him about as i am happy for him to do it:) i guess i want to re-phrase - i just kinda want peoples opinions on the subject . .

but thanks

Only he will know. Maybe he thinks he can penetrate deeper that way or it is natural for him to put his hands there and does not realize he is pulling your cheeks in the process. He might also want to see your butt contract when you have an orgasm. With men you never know

Knowing men I will be suspicious that it is the first step to anal sex or slipping a finger in there....

I have noticed guys spread my cheeks in doggie also. I am not sure why they do this but my first quess would be that he is trying to make his penis penetrate deeper. I say this becuase it seems like they start out either with no hands on me tagging my butt cheeks on every thurst or he has his hands on my hips pulling back as he thurst which seems to make him bump my cheeks. I seem to notice it is after a while of this that some guys began to spread my cheeks maybe trying to move it out of the way.