Thank you for the added information.
It is likely that you have developed an infection known as Bacterial Vaginosis
(BV). This is not an STD but occurs due to a overgrowth of bacteria like gardnerella. Gardnerella is a normal bacteria of the vagina but under certain conditions when the ph of the vagina changes, it can grow too much and cause inflammation of the vaginal walls. This will cause pain.
A common cause of Gardnerella overgrowth is use of antibiotics. Antibiotics can kill off healthy bacilli of the vagina like lactobacilli which keeps the ph normal.
Treatment s with antibiotics like metronidazole or tinidazole which prevents overgrowth.
A greenish vaginal discharge is seen in a an STD called trchomoniasis. This condition can not only cause pain but also itching of the vagina. Although you have been married for a long time, if metronidazole dose not help decrease the pain, you will need to get this checked out.
To decrease the burning, you can use a vaginal moisturiser like Replens, available without a prescription - it will decrease the dryness and inflammation to some extent. You can also take an oral anti-inflammatory like Ibuprofen.
I hope this helps.
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