I don't seem to be able to Maintain an Erection and I get a sore pain in the center of my Penis.

Hi I am 32 years old and I have had an issue since I was 29 but it seems to be a bit worse or so I think. At 29 my erection strength reduced and I will still able to ejaculate fine however after I would feel sore all through the center of my penis. Over the past year I have put on a bit of weight and breach into the overweight category but just on the tip of it. I am trying to lose weight and exercise however when I am with my new girlfriend I can get erections but it seems I can't maintain them always and I can't always get erect when I get aroused (we haven't had sex yet). Our relationship is new and I don't want to tell her about this yet because I don't even know whats going on. My local doctors are terrible so I need to be able to tell the doctors exactly what's wrong and the course of treatment because they are that bad. I just want to know why this has happend and if it's possible to fix, i'm guessing there is more of an issue as it hasn't repaired or whatever in all those years. I did used to go heavy on masturbating when younger.

So to start with the last point first on masturbation: if you are talking about years ago, then unless something occurred to change how you penis looks, or you stopped producing semen, something of this magnitude, then this would have no impact.
Unfortunately, if you are overweight, or you do not exercise a great deal, this will have some impact. So, for lots of men once you get to late twenties and early thirties the strength of erections can reduce. This is particularly true if you drink alcohol regularly, have a poor nutritional intake, or you are taking medication or using recreational drugs.
Doctors are likely just to prescribe you drugs that can help with strength of erections, and suggest you do something about your weight, and lack of exercise. The thing to do would be to look at a wide range of things that improve your general health and level of fitness, and perhaps radically overhaul your nutritional intake.
In terms of age related stuff my main suggestion would be on concentrating upon what goes on before sexual activity takes place, being relaxed and in the right state of arousal can be critically important. Indeed, there is no harm in practicing the many ways in which you can give and receive stimulation even before sex takes place and simply the natural point at which sex takes place simply is a natural occurrence. Be ready in advance, if you are going to use condoms make sure they are to hand, rather than getting to ‘the right point’ and have to go no further because of the lack of protection.
If you think it will help, go see the doctor anyway …