Trying, gently, I'd be very leery about this "need to be alone".
I've read your other posts and from that small window into your world it seems like you are doing everything but cartwheels to try and keep your relationship together. That's just not a recipe for long-term success.
How exactly does he plan to "work on his issues"? Is he in IC?
Are you in IC? You mentioned trust issues in a previous relationship; now there's this (the specifics of which you do not seem to have given; sorry if I missed it). The betrayed partner is NOT responsible in any way, shape, or form for betrayal. That said, there are situations where traits he or she brings to a relationship increase the vulnerability to being in the wrong relationships. Low self-esteem, naivete, excessively trusting...all can wind up causing problems....this is in addition to the issues introduced to an existing relationship by betrayal.
Just remember you are worthy and deserve a fulfilling and healthy relationship that doesn't revolve around accommodating your significant other's needs. If you're having to do so at what's the "easy" stage of a relationship (not living together, no children together, etc.) it's a sign you can do better; a sign that's wise to heed.
Best wishes! (((Trying2013)))