First, I would recommend therapy. A therapist can help you understand why you are in this pattern and how to break out of it. A therapist can also act as motivation. If you decide to take a step, knowing that the therapist is going to ask you how it went can help you take that step.
Second, there are lots of ways to meet people. I really like the meetup.com groups. These are groups of people who have shared interests... in my area several of them are very good. There is also church/mosque/synagogue (if you are so inclined) and charity groups. And you can also take community classes in most places.
Third... work on meeting people as friends and building a social group first, then it will be easier to get a girlfriend. It is a lot easier to start and build a good romantic relationship once you have a social group.
Fourth. I have found personally that physical exercise is a very good (and healthy) anti-depressant. This is also backed by science. Find some physical activity that you can enjoy... maybe running, yoga, working out all of these are good. For me it is my bicycle. Exercising enough to get your heart rate going fast for 30 or 40 minutes is really good.
You might be able to find a form of exercise that can also work as a social activity. Running and biking are both very good to do with other people... and often in cities there are organized groups that make it easy to meet up with people.