Chase has asked me to come and see if I can help you and your husband with this issue. From what you are describing it sounds more like a emotional issue then a health issue. If he is able to sustain a erection but is experiencing premature ejaculation this has to do with his age and ability's not his diabetes. While diabetes can cause erectile dysfunction he would not be able to sustain a erection at all.
Since this is not the issue, it sounds like you and your husband have gotten into the rut of life. There are a couple of things I would recommend in this situation. One is speaking with him, sit down and let him know how you feel. Let him know it is not all about sex but that you really need and want to have this intimacy back. Remember communication is the key to any locked door. Your husband may be feeling a little inadequate since he is having difficulties with premature ejaculation so you will want to broach this subject carefully. I would not even mention the premature issue right now. I would mention that you want to change things up a little. Ask him if he will give a little......explain that you understand how he feels and would love it is he would try to understand how you feel.
Try different things, this can include letting him know earlier in the day that you want some intimate time. Make plans by having a nice dinner and a early night in. Let him know you want to start only with cuddling and kissing. Do not be afraid to tell him what you want...........rember sometimes us men can be a little oblivious to what you really want.
You may want to consider speaking with him about talking to the doctor, there are medications he can use even with diabetes such as Cealis....this is not like Viagra in the difference of it helps him to get in the mood with stimulation. Often this medication can help to get him in the mood easier and more often. One dose often can improve his sexual mood for up to three days.
It is good that you have not cheated.......keep in mind that it is not fair to your husband nor yourself. If you feel that you need to do this, then you need to be honest with your husband. I know it seems easier to just go and cheat since he is not providing like he should but the fact is you are not being fair to him or yourself. If you must cheat consider being honest first.........give him a chance to make this right. Let him know what you want and what you plan on doing if you are going to do it regardless. While this will hurt him badly it will give him the opportunity to take this matter more serious.
Though I would remind you that you must accept the responsibility's and consequences of this action.......he could very well leave you. But better to leave and be done then never give him the chance to fix this. Something you should also keep in mind....while sex is not a foundation for a marriage it is important. Are you willing to lose your marriage over this? If so then it is time to make some serious choices. I can not tell you what to do but I can tell you that you must be fair to your husband and yourself in this matter.
I wish you both the best, XXXXX XXXXX is your first route in this matter.