Mental tension. What should i do?

One can understand the situation you are going through and it is not as easy as said. You said that you are separated, but you haven't mentioned if you completed the legal formalities of divorce.  With the difficult situation of being separated it is common to look for affection, care,  feel secured that made you to get into another relationship.  You don't have to feel guilty. Now the challenge is that he would get married to someone else. You mentioned that you can't live without him but you haven't expressed what his feeling is!!! If he is also feeling the same intimacy and care towards you then you  both should take the next step of coming to an understanding and conclusion, in order to get married and lead a good life. After all, it is your life and you both must live happily together. There will be challenges from parents that you need to handle with assertiveness and convince them. In the contrary, if your friend is not serious about the relationship then you need to do an introspection about yourself and see what would be good for you and move on. You about residing just 33 years old and surely you will find a life partner to continue your next part of your life. Seek help of a Counsellor in your city for professional help. God bless