Not good. You always move forward faster than retreating.
Besides, moving back, is almost a freebie for your opponent to throw leg kicks, its pretty tough to be moving backwards and getting a check in time.
Besides, if you keep that style up for the duration of the round, you'll lose on ring control, and maybe aggression, as they are tied together.
If your opponent overwhelms you with combos, you need to interrupt his combos ASAP, the longer you wait the worst of a strike you'll eat eg. liver kick, flying knee, etc. Try not to let your opponent get more than 3 strikes on you.