Your mother is scared of being alone and of losing you, so she frightens off any girl who comes near, giving silly excuses.
You feel responsible for her, so you give in, live with her even though you are 29, and are willing to give up the chance of a wife and family, so that you can stay with her.
Your mother doers not respect your right to a life of your own, because she wants to control your life, so that she won't be lonely and vulnerable.
You say that you are a capable guy, yet you are allowing this to happen, by not being assertive.
Most 29-year-old men have left home. It isn't harsh, it's the way things usually work out.
Is this how it is going to be ~ for you ~ for ever?
You need to sort this out.
If you can't speak to your mother, clearly, yourself, then could you & your mother go to family therapy?
Are you not able to speak to her, plainly, and say that you will always ensure that she isn't left alone and vulnerable, but that she must not interfere with your relationships?
She controls your life because you allow it to happen.
You don't need to be harsh and nasty. Your mother is obviously very fearful, and this needs to be acknowledged, and she needs to be reassured that she is loved and will not be neglected. But I feel that she also needs to know that you cannot accept your life being controlled and will not tolerate your girlfriend being threatened.
The alternative is that you and your mother live together ~ just the two of you, exclusively ~ from now on.
The choice is yours.
Good luck!
PS. Some more background might help:
How old is your mother?
Does she have health issues?
Does she have many friends?
Does she have other relatives?
Are you an only child?
Which country do you live in?
Do you belong to a culture where this sort of behaviour is traditional for mothers?
Does your mother belong to any clubs or organisations?
Have you suggested counselling for your mother?
