Returning a serve spinning into your body

Hi,

These days I am having trouble with a particular kind of serve. When playing doubles, my opponent (who is right handed) does a backhand serve, where he moves his bat forward (to give speed to the ball) and towards the side, which generates side spin. In other words, it is almost a lefty's normal fast topspin sidespin serve to another lefty. Now, being a left handed, the ball has the tendency to spin from my left to almost the middle of my body. If I pivot and try to play forehand topspin, I am not able to control it, the ball goes over the table. My backhand counterhit is not very strong, but if the ball is high enough, I can hit it back, but otherwise, that shot also makes the fly past the table. What do I do? Normally, if the ball didn't have much speed on it, I would easily return it using a forhand flip or push. :(