So your problem is you take to long to cum and she cums to fast.
Well, to help you out in cumming faster just get her to do more of what you like and to suck you off really good and you should cum faster.
Also if your up for it she could finger your ass a lil as that will help things out.
As for her, well how do you eat her out. I mean if you go fast and hard on her that may be why she cums so fast and if that's the case go a bit slower. Also are you sure she cums, like she isn't faking it?
As for the fact you do oral on each other due to past pregnancy scares well you can always do her in the ass since your too scared to be in her
pussy because of what could happen.
But I say you should get off just doing oral on each other and just use lots of protection to insure she don't get knocked up by you.