First of all, how old are you? if you mind telling us? I dont think it has anything to do with you doing jelqs or any Penis Enlargement whatsoever. It can have different causes, physicial causes or mental causes. Even if it is your wife, there may be times you just dont get aroused enough by her and it might work the other way around as well.
Do you exercises whatsoever? I mean fitness... if you dont, I suggest you to start, when you exercise you rise your testosterone level up, which is good for erections plus it makes your body fitter which makes you better in bed. Ignore it only when you are a Gladiator already.
Do you smoke? do you eat junk food? if you do, try to stop or lower it to minimum, especially with junk food. Eat some proper food, fresh good meals, eat more fruit, drink more water.
Drinking a lot of water is really important when it comes to erections, you will be going to pee more often but it will make difference, when your body is well hydratated it works better. Make sure do be a bit outside too every day.
Eat raw cacao nibs, get it into your breakfast, yoghurt or whatever you might eat, and Im not saying chocolate, raw cacao nibs
Personally I recommend the warrior diet, make it your lifestyle and you see a big difference. If not, just make sure to watch what you are eating and when.
Also, try something new in bed, what you have described, sounds like the lamest act of sex you can think of, get creative, wake your wifes naughy girl in her, get passionate, make her shiver like never before. She will like it and you will like it. And wearing a ring wont help you much unless it is used as a recovery you can read in the [words=http://www.mattersofsize.com/forum/showthread.php?64036-My-Best-Work-Ever-Penis-Enlargement-will-Be-Changed-Forever-gt-gt-Gain%20inches%20with%20SRT-Theory-and-Routine]
SRT[/words] method DLD wrote about in another thread. Maybe try it too?