Sewing machine Bobbin thread tangling. Top thread keeps breaking.

The top thread is probably breaking due to the bobbin thread tangling.
First-off fit a new needle .... do that anyway ! And if you haven't recently cleaned your machine (and you should do it every week as a minimum), clean-out under the stitch plate, remove the hook, clean the hook race and give it a small drop of oil, even if you're using the lightweight plastic hook/shuttle. Check that you have adequate bobbin tension ... when you pull the thread out of the bobbin case there should be a bit of resistance --- technically, this should be set-up using the correct tool and a set of weights, but if there is no, or very little resistance, you need to increase the bobbin tension a little bit at a time using the small screw that holds the tension spring down onto the bobbin case. This is a very fine adjustment, so you may find you only need to turn the screw less than a quarter turn to get it right. Ensure that, when you thread the top thread up, you do-so with the foot lifted so that the thread goes down properly between the top tension discs.If you're still not getting anywhere, check the basic timing/needle depth by looking at some of my other posts on the subject.