Yes, that is not good. You really need to get after him and stop this now. If you do not have a lot of horse experience, and are afraid, you should hire a professional. It can be dangerous to get kicked. He will also be able to feel it if he scares you.

So you need to think in terms of horse language. If he raised his leg at a dominant horse, that horse would bite him, or kick him, to put him in his place. You can not bite him, or kick him, so I would use a lunge whip. Use a long lunge whip so you can swat him and not be in the range of his legs. When you enter the stall, or pasture, and he raises his leg, pop him hard on the rump with the whip. Scold him in a firm voice. If he kicks at that, pop him again. That is what a dominant horse would do to him in the pasture. You have to be the dominant one. I know this sounds tough but kicking you, and injuring you, is not so nice either.

Make sure yo praise him then when he puts his feet down and is good.

If you do not feel comfortable doing this, then get a professional to do it.

Spend a lot of time with him grooming and such so he does not just associate you with the whip. When you go to catch him, have a treat so he leans to give you his head, for the treat, rather than his hind end. Unless he starts nipping, then do not feed him out of your hand.

If he is not gelded, you may want to have him gelded as well. It will make him a less dangerous horse and easier to be around with out the raging hormones.

Be careful and I hope this helps.