Since the OP has been reluctant to offer up more details on the specifics of the problem - where his/her timing starts to break down, and in what manner and under what circumstances, you are probably right. All this generic stuff like "use a metronome on 2 and 4", "set a drum machine to leave you high and dry for a few random measures", or "get a click track from youtube", isn't really going to be much help. Especially if the issue is related to, let's say, dynamics (ok when pp but less good when ff), right-hand position (ok when s.p. but less so when s.t.), left hand shifting, string crossing or something else. Without that information we are but words on the web, therefore "get a good teacher".