This is a nice, positive thread about "the problem" isn't it?
My libido went on holiday without me about 6 years ago - it's sent a couple of postcards, but doesn't seemed to have booked a flight home yet! Mind you, I'm single, have ishoos & am on antidepressants so what can you expect? I should go on holiday, too!
Thinking back to previous relationship hiccups - and my near-encyclopaedic knowledge of diet & nutrition - here's what I can offer ...
Most of the time, as many have said, it's to do with habit, feeling 'mummified' and de-prioritising sex. Dates are a necessity: you need to go out for meals & drinks, so as to get the communication thing going again; it's also a great idea to go to the cinema, theatre, exhibitions or whatever. That adds a few credits to your "shared experience bank" and gives you something other than kids & bills to talk about.
Have your hair done, fix your nails and buy some pretty underwear that fits you properly! Makes more difference than it should ... to you! Any benefits to him are incidental
Go back to playing. Not with the kids - but, way back when, did you get tiddly & dance round the kitchen together? Go bowling? Play stupid guessing games to pass the time? You know ... mess about together.
Add new dimensions to your own life. Pick something to study, volunteer, or put yourself about for some freelance/part-time work. Being a mummy may be your priority, but has your brain gone away with my libido? Thought not.
If sex made you hurt (sorry to hear about your sore episiotomy, above) go to your doctor and whine until s/he does something about it.
Zinc and iron deficiencies are very common in Northern Europe. Both make you feel tired & apathetic. Another mineral in short supply is selenium, which is thought to affect the libido. Start taking a multivitamin & mineral supplement that has everything in it. Holland & Barrett's Super One is quite good. You also need huge amounts of Vitamin B (all varieties, and way more than the RDA). The Super One includes plenty of Bs.
If you like Marmite, it's an excellent source of trace elements and B vitamins. Get your 5 fresh fruit & veg, or take a high-dose Vitamin C. In fact, you can't overdose on C (well, you can, but not in the real world) so there's no harm in getting extra. Nuts, especially Brazil nuts and walnuts, are good for your zinc & selenium levels. Whole grains are good for Vitamin E, which is also thought to help your sex drive (and your skin).
On the weird & wonderful side, there's quite a bit of evidence that ginseng and ginger help with energy & enthusiasm. You should make tea with fresh or bottled root, if you can get them. Ginseng root is scarce & expensive, so most people use supplements. It would be hard to overdose on those two; go for it. Other Oriental herbs that might help are Gingko Biloba, Devils Claw and Horny Goat Weed (honest!!)
Finally, hot spices have long been thought to pep up the urges. When you go out for that meal together, how about making it a curry or a chilli?
Watch a film featuring plenty of good-looking sex (that rules out porn, then ), read a bodice-ripper, get your fabbest shoes out from the back of the wardrobe ... and good luck!