Re: 1.5 months into relationship - no sex.
Next time you get resistance to the point of physically stopping you, have an honest to God sit down talk with her. Hint: you don't have to wait until she stops you; you can bring it up. Women love when their man wants to talk to them. Tell her what you expect and why you expect it. Tell her you have needs that are not being met and you would like them filled with her, but will go to another woman if she isn't willing to perform. Explain you are happy being exlcusive with her, but would rather be single and come over to cuddle a few nights a week than be in a relationship where you aren't completely satisfied. Ask her why she is resistant. Ask her what she has done in the past, what she's willing to do for you and why. Listen. Do not respond disfavorably no matter what she says.
(You haven't given us enough information to really help you beyond this. Perhaps, you can will us in on what you know of her past, your past, your ages, how you met...)
The truth of the matter is: a relationship means both of you have to give in to some things to make it work.
If you talk to her and she offers something, stop her. Tell her you want the first time to be super special. Tell her you want her to enjoy it, but be very open minded. Cuddle and start planning the most romantic evening and sexual fireworks you've ever devised.
Until you give more information, I can't offer much more to you, personally.
I have failed more than most men have tried.
Every woman you pass up is a woman you will never have.