Lowering levels of oestrogen can weaken the bladder resulting in having to go more often.
Unfortunately, drinking less can actually make the symptoms worse at night.
Dehydration concentrates the urine in the bladder making it more acidic which can then irritate the bladder making you want to go (this can also cause more bladder infections!) so drinking plenty of water every day is really important.
Just avoid tea, coffee, sugary/fizzy drinks in the evening as they can irritate the bladder as well.
You could also start doing the Kegel Exercises as these help to strengthen the whole pelvic floor resulting in better bladder control. Just Google for instructions.