Unfortunately this type of infection is so common in menopausal women. It's probably just a coincidence that you started using the liners. Were they the scented ones?
When I had my last infection my doc said that no matter how careful you are some people are just more prone to them.
Cranberry will not kill the infection, but it does stop the bacteria from attaching to the lining of the bladder. So it is more of a preventative measure.
Some tricks I have learned to prevent infection are:-
1) Don't get dehydrated.
2) Don't delay going for a pee when you need one.
3) Make sure you sit on the loo and not hover (difficult when out as who wants to sit on a public loo)
4) When you have finished your pee, just sit there for a minute. You may find you then do an 'after thought pee'. It's this left behind pee that often goes stale in the bladder and causes the infection.
5) Avoid biological washing powder.
6) Avoid tights.
7) Cotton only knickers.
Some of there were told to me by doctors, others I have found out myself.
I hope this helps a little, put do get to the docs as antibiotics are the only cure for an infection.