Does it climb and twine round things? Look on Google images for Calystegia sepium. If that is what it is you should get rid asap as it grows very rapidly and chokes everything. It has very deep but brittle thick white roots (nicknamed Devil's guts) which are almost impossible to eradicate once they get a hold. Try to encourage it to twine round a garden cane and when there is plenty of it there lay the cane down flat, protect any surrounding plants and treat it with glyphosate. Note what the new shoots look like and remove any small ones as soon as they appear. A pity when its so pretty but if you don't do it you will soon be wishing you had!

Without a photo we're playing guessing games. Might be bindweed, might be all sorts. Please could you try again with a photo?

Agree with Beattie we need a photo, otherwise we are guessing in the dark...

Sounds like the bindweed in my next door neighbours garden.