Should I have an affair or can someone suggest another option?

My wife and I have been married nearly 25 years. While she never wanted to have sex as much as I did, she used to enjoy it and would even enjoy dressing in the lingerie that I would buy her. She seemed to enjoy trying new things and even dressing up in a costume occasionally. She is a beautiful woman with a very sexy figure!
Now, though, sex is like a chore to her and if I don't ask, it won't happen. When I do ask, she will often say no and ignore me. When she agrees, it is often that she is upset about it and wants to "hurry up"! There is no more lingerie, and it is the same 2 positions (mostly one) all the time.
I feel like I do not matter that much to her anymore. Even the little things are missing. Things like holding hands, cuddling, a hug, kissing.
She hates to talk about it and I want to figure it out.
Meanwhile, I have been approached by a friend who is in a similar situation and she has made advances to me.
I am very tempted, but don't want to be a pig!
My wife is not having an affair (99% positive) but just doesn't have the needs that I do! I'm tired of being ignored and very frustrated!

What should I do?!

Same-Sex Marriage