I don’t normally get involved in relationship questions – since there’s no absolute right or wrong answer, but your predicament moved me to respond.
You have managed 18 years together, many don’t even make half that – so you must have something going for you. But that your partner has not made love to you for such a long time does not bode well. I can understand how you feel, (although I’m a male), it’s a fare bet that you do the lions share of the housework, with both of you going out to work.
I like Brinjal’s suggestion of taking a holiday away together – but you both have to agree the objective of the vacation, otherwise there’s no point. If you do try a holiday, try to make getting to your destination as stress free as possible (even if this involves putting yourself out, for the sake of working things out). It need not be a holiday abroad, but a relaxing long weekend at a good hotel – maybe one that you have stayed at together in the past, during better times. But it sounds like you will have a job getting your other half to agree to such a holiday.
As a last resort, I would have an honest heart to heart with your partner and lay your cards on the table. Making it clear that if he wants nothing to do with you, then you want out. This will force him to decide what he wants.
If you do nothing, then in 6 months time you will be walking out. Have you really thought what this would entail in terms of new living arrangements etc, and the inevitable increased costs for each of you in these tough economic times?
Whatever happens, I wish you the best of luck, but in your situation I would be very reluctant to give up on an 18 year relationship without giving it my best shot at making things work. The grass may look greener on the other side – but it rarely is.