The thing with masturbation and/or porn is that sometimes guys get used to a certain level of visual and/or manual stimulation, and then nothing else will do it for them. This might be the case with your BF.
Clearly there are other underlying issues like the depression and the after effects of the drugs, but it doesn't really sound like he's trying, and it's convenient for him to say that it 'might' be you.
Is he interested in making things better for you both? Or does he expect you to live a nun's life? If he doesn't then ask him to have a full physical to rule out any other problems - hormonal or otherwise.
He might start by stopping with the masturbation and the porn and connecting with you sexually, rather than with his hand. This will probably take some time as he'll have to re-learn what he finds sexually stimulating. It's sort of like he'll need re-training.
However, and this is the bad news. SSRI's, can in some cases, cause loss of sexual function for months (or years).
Post-SSRI sexual dysfunction - Wikipedia, the free encyclopedia
I suggest that he should also go back to his shrink and talk about what's happening.
Good luck.