Sounds like they got reach over yours and they control your distance with it.

Hell, have some fun with movment,if your getting tagged anyway

If they are bigger with longer reaches or controlling from behind a solid jab;

Go low ,weave and make them hunt you and you go under that lead arm ,close in under their lead arm,and pop up in 'your distance' and throw.
Or close in on their lead arm and choke them up (mes up their distance),just stay away from their rear arm and close the cap safley.
A short shuffle in the same stance will close the gap as you throw ,over the top of or around their extended lead arm.
Timing ,they poke out a jab you follow it home as it retracts and close on it, throwing again moving into new angles the whole time.
Go under their lead and throw a straight shot up the centre as you go under.
Start moving around more,make them shift to you and tag them as they adjust to you.Smack up the openings you create in between their adjustments.Throw as you move,throw from down low as you move in too. just plan your actions to one side of them at first (their weaker side).Close,attack and move away from their rear arm,all at once and then catch them again as they adjust to your new position and move again, throwing from all angles.