mimumonschein - I am not a doctor and I can only speak from my own experience. My understanding is that ‘thrush' results in a cottage cheese type of discharge and makes the area sore and itchy. Bacterial vaginitis will be a bacterial infection which often clears by itself but sometimes needs ABs. However, when the menopause arrives the body simply doesn't have the correct flora balance in the vagina to repel these problems - the natural secretions dry up, the skin becomes fragile and this is why local oestrogen like Vagifem with vaginal moisturisers alongside can help to reduce the chance of infection. Sadly many GPs and even gynaes are ill informed about these issues but here on MM many of us know that women struggle with these problems on a daily basis.
Often these vaginal infections do come under STIs and it is worth going to GUM clinic to have a full round of tests as they may be able to offer treatment options and advice - also reassurance. You should have a GUM clinic somewhere in your area so google this and generally you can just turn up without a referral from the GP.
Just one more thought: Do you struggle to keep your weight under control? Have you tried cutting as much sugar as you can out of your diet? Do you suffer with constipation or diarrhoea? Sometimes poor diet, lack of exercise and excess weight can make things worse. DG x