Very valuable responses so far.
Makerhergocrazy described very well how you should start with kegels. I also believe that kagels can make a huge EQ improvement and i have seen it myself. A lot of men have given great feedback on how kegels affected their sexual performance and studies shows that they are a good treatment for ED.
My opinion is that your issue is definitely mental. This can happen to me occasionally and i am in a perfect shape and young.
Its a signh that you maybe are too much in your head and you think of it during sex. Concentrate at the passion of the moment and do whatever turns you on can help.
Even if you are experienced in sex, 5 years is a lot of time and this can influence your performance. It will be solved naturally, just don’t be harsh on yourself and understand that is a very common and temporary thing.
Kegels are anyway something that all men should do.