I have a friend, her biggest life regret is moving away from her fiance whom she was unable to marry due to religious differences / problems.
I can't state clearly enough, that if you let work or religion dictate your heart you will come to regret it unless you completely and utterly have faith and belief in those things to the point where you trust in them over your own heart. That is something rare.
My friend, she moved away because she couldn't deal with staying around the problem. Now, I have my personal oppinion but as hers is somewhat more "informed by circumstance" ill let you know that she regrets moving away. Regrets the outcome (he married someone else and now has his own family) and she is now living her life in what (to me) is a most strange and highly practicalised manor (since she already met the person she's now convinced was / is the love of her life so she's trying to find a new way to decide whos right, which is sad IMO).
Now, my oppinon is, that this guy was pretty useless. It was him and his religious obsession keeping them apart and refusing to see my friend for her and her own needs. He's not a bad guy, he's just messed up by religion. Having faith is a good thing, but you either need to put complete faith in faith or put complete faith in fate/love. Trying to split things causes a mess.
Decide what you want to believe in (think it through) and go with it, do so by thinking everything out, know the arguments for and against and be ready to believe wholely in whatever you choose (know why you choose it and make the reason one which will stand up to any storm.. make it something REAL).. and remember if you choose something or someone mortal, make _certain_ they are worth your faith. A god letting someone down is bad, but you can always find a different way to see things...
Its a big ask.
Now.. if he is voulentarily seeing other girls, and you have said nothing which suggests your relatioship will not be going places (e.g. Marriage/Children/Together Forever just the two of you in the romantic vain) not given any indication you feel less for him. Then he cannot really seriously be deeply caring for you as he would not wish to hurt you. Even if its happening by "mistake" because you have been away, it should be spuring him to try and arrange getting together with you.
If you haven't been giving him the "this is serious" signals, or you've been unsure yourself. Then its fair enough. You need to decide where you stand, and by the sounds your very involved to the point you wish to continue in a mutal partnership exclusive of third parties.
So to sum up... decide where your at first and foremost. Second, communicate clearly and unequivicably to him your position (e.g. be vunerable, part of love is taking a big risk of being hurt) and lastly, make plans to be together in a ongoing way if you find your both serious / commited.
Him seeing other girls is a real bad sign.
Wishing you luck.