We if it seems all yucky to you and just thinking of it creeps you out then don't do it if you don't want to, you shouldn't be forced into doing anything that you're uncomfortable with doing. If however you're willing to try it then just make sure you take in the advice people are telling you i.e. use lots of lube and take it slow etc etc. If you're doubting doing it then maybe it's a sign you should wait..? at least until you feel more comfortable with doing different things like that, if you ever think you'd come around to it I mean .
Well, you are in every right to say no! I would agree with you, if its a heterosexual relationship, theres no NEED and its sort of not the most natural thing!
Just dont feel pressured, whatever your decision. Just because sex is getting increasingly more drastic, it doesnt have to be something you partcipate in!