A few questions for you. Does your wife have a job/hobby outside of the home? Does she ever get time to herself away from the kids? You mentioned her having low self confidence. Have you encouraged her to take a healthy cooking class with a girlfriend? Or have you maybe taken the kids away from the house for a day and let her have a day completely to her self?
Maybe she just needs a little time away from being wife/mom 24/7. Then maybe time spent together will be a little more fun. Be spontaneous. Tell everyone to pack an overnight bag and go to the local hotel with an indoor pool and play for a day. Eat take-out pizza in the room. Anything! Just get out of the rut you are in.
Oh! Don't forget to pray. A lot! :o)
Good luck to you!
One last thought.
Try sending her e-mail love notes. Nothing long or complicated. Just something to let her know you are thinking about her during the day. Maybe a link to a travel website or vacation spot with a sentence saying you wish you were there with her right then! Or join her in a chat room. Conversations tend to get a little spicier if you're not facing each other!