erection problem I am not getting any sexual feelings.

All sexual activity begins with the most important sex organ - the brain!

If your head isn't connecting to your other bits and pieces it isn't likely you will be able to perform. Clearly the connection is there as watching porn produces an erection and you feel the need to masturbate sometimes...

Your problem probably has more than one facet...
First, you are probably someone with a naturally low sex drive.
Second, you probably have either conscious or sub-conscious concerns or stresses about anything from your performance, your wife's opinion of you, fuel bills, taxes, children or any of a host of other things that can make a penis withdraw into safety...
Third, it is possible the problem is connected to something in your formative years - anything from overhearing a chance remark to a bad experience...
Fourth, it is possible that ordinary sexual encounters do not arouse you and you might need the extra stimulation of something like role play or you might have a (as yet) unknown fetish...

OR it could be any combination of all of the above plus a few other things...

I strongly suggest you talk openly and discuss all this with your wife and invite her to try and stimulate you with her hands and mouth, experiment in a little role play and a little light bondage and perhaps a little gentle sado-masochism...

Perhaps watching your wife perform for you with a toy might do the trick?
How about introducing some porn into the bedroom so your wife can have the benefit of the resulting erection?

There are many mechanical erection aids from pumps to constrictions - one called a geskell is said to produce good results and is made up of two leather straps and some strong bristles: but the principle is the same in most of the variations of the constriction - the blood to engorge the penis is supplied through internal vessels and escapes back into the body near the surface. Provide a constriction near the base of the penis to reduce the amount of escaping blood and the penis begins to erect...

Viagra is one of the chemical aids to an erection...

You say you have to force sexual thoughts into your brain - lots of people need to fantasise about sex to kick-start the action and others fantasise while actually having sex...

I feel you will probably need some professional counselling to discover whether your low sex drive is natural or whether it is inhibited by something from your past.
BUT please begin by talking openly and honestly with your wife...