You sound like someone that is new or fairly new. If so, you have to keep practicing. And some of that practice should be working with your sparring partner on things like this. Contrary to what some think, there are many different kinds of sparring. Some is all out, but some can be a partner using a technique or set of techniques and you working to counter it until you figure it out.
I'd also suggest you talk to your instructor, and/or senior students in the class. They should help you.
And finally if you're fairly new don't be frustrated. I've trained for many years and always find things to work on.
Incorporate into your training skipping rope and doing some footwork and distancing drills and learn about beating them to their set point and using angles and probing. All those things help hold the key to you breaking down the distance better against a taller opponent and closing that gap that you are having difficulty with. Usually no one thing in itself will help you to do this but instead using a combination of things is what I have found when fighting someone taller.
Doing this will easily take several months so don't expect immediate results to start with. However if you start working on these things and developing your knowledge and understanding of them then in several months then you should see a change in things and how well you are able to deal with fighting a taller opponent.
Have you tried moving laterally? Or circling? You don't need to move in a straight line, after all. You shouldn't. It makes you predictable.
How about, you know, blocking the kicks, too?
kick em in the balls
When I fight people my height or shorter I do okay, but today I had to fight a really tall person and when they kick at me I can't seem to avoid it by stepping forward or backward. Also when I try to blitz them they just kick out and their leg knocks me like all the way back.
