My Boyfriend And I Used To Have Really Hot Sex..for A While Now Our Sex Life Has Gone Down. We Have Both Gained A Little Weight But Other Than That Everything Has Gotten Better Except For The Sex. He Says Its Not Me But That He Has The Problem?

That is not a good sign.
What does he say his problem is exactly?
It is abnormal for a guy to completely not want sex.

There can be many issues but all have one cure. Do it more. Make it fun. Experiment. If he needs a pill then get it. Now to know where the boundries are. Introduce porn into your lifes. This is a great way to find what he does and does not like. I.E. If he is looking at lesbians then he probably would be receptive to a threesome. If he is looking at images of bieng tied up then surprise him. The further you are willing to go the more he will be into you.  Remember the bedroom is not a place for shame.

He could be having rectal this function

Cause he is sucking your boobs

Maybe he has a disease or something that he's hiding from you, is having an affair and is no longer interested in doing it with you, or has moved on from sex.  My parents had some sex but now that they are older no longer find the need in their relationship for sex.  Whatever you do, don't assume the worst.  In fact, don't assume anything.  Confront him. 

Yes. It is a problem with low testosterone which caused low sex drive. Give him Optimale RX, it worked for me. He will have better sex drive. www.checkmytestosterone.com

I think yeah.stop doing sex maybe you will pregnant!

Welll I Think Find Another Man And Test Them For Sex And Just Find The Right One Who Plays. And I Think His problem Is Hes With Another Girl...

How old is he? It maybe because of the changes of his testosterone level. MaleEnhancementGuide.org will help you to understand your boyfriend or maybe you can share with him to have a sex life more exciting.

Then do a sex again

Or you could just ask your boyfriend if there is anything new that he wants to try in bed, I guarantee you that his dick will stand right up when you say that.

This is normal.  The "fun, new and exciting" stage is over.  Now is the time you see if it's true love, or just a fling.