Bic pencil problem? Does this happen to you?

If this is an automatic pencil and it's the first one you've had, have you changed the lead? When the lead gets too short and isn't held by the pencil anymore it will fall out a bit when you put it lead down but shrink back when you press it to paper. Change the lead.

If it's not the lead, just check the inside of the pencil, when putting a new lead in, hold the button at the back and push the lead in through the nose. See if it grabs. If it does, you can use if, if it doesn't, pull the lead out and see if it's broken. Sometimes lead will just break.

If it's not either of those see if there's anything stuck in the mechanism that looks like a blunt claw (it opens up when you press the back of the pencil and when you let go closes but has a tiny round hole in the end). This pegs the lead in, and if it's being held open by something your lead will just slip out and back all the time. You see this bit if you unscrew the cone bit where the lead comes out.

All else fails, you need to get a new one.