C.,
The first thing is to have confidence in the fact that you are the mom and have the right and the duty to discipline your son. Don't shy away from discipline because you don't want the reaction that follows. And remember not to take the reaction personally.
He might be acting that way because he is angry with you for trying to stop him from doing whatever he is doing. He sounds like a child with a strong will and determination. These are very wonderful, admirable qualities, but can take a lot of strength and determination on your part to help him channel that positively.
So, when he strikes at you, kneel down and look into his face and say firmly, yet calmly, "His name, you may not hit Mommy." and then sit him in time out for about 1 minute. (I always did about one minute for every year old they were). Then after the minute is up (which will seem like an eternity to him, you can even set a timer and tell him he can get up when it beeps) then tell him that he needs to apologize to you. Even if he isn't speaking much yet, he can still hug you and be repentant.
Then the next thing to remember is that just because you did that, doesn't mean he won't do it again. He will. He will continue to do it many more times, but as long as you are consistent each and every time he strikes you in retaliation, he will eventually get the message. Or he might do something else instead (like kick, or spit) and if he does, you do the same again.
I also developed what I'll call "mantras" for a lack of a better term. They were sayings that I seemed to automatically answer with or say to the point that my kids got sick of hearing them, but they were very worthwhile in their training.
One of them was, "When you ask a question, the answer can be yes or no." That meant, "You may not throw a temper tantrum or any other such thing just because I say no to you. I am the mom, and I have the right to say no." I did not allow my children to have any reaction except obedience to what I said (as in, no stomping of feet, no eye rolling, no negotiating, etc.), and if they did, they went to time out or to their room or they got whatever they were asking about taken away. Your son is too young to understand that mantra now, but if you start using it anyway, he will begin to understand it little by little.
Another one is, "I am the mother and you are the child. You must obey mommy." (sometimes, like in the store when they were standing up in the cart, it would be shortened to, "Name, Sit down" and if that was ignored, then "You must obey mommy.") This just establishes your rightful authority over them and makes them secure in the fact that boundaries and relationships are established. I remember saying that so often when my daughter was one years old that one of her first words was "obey".
Also, sometimes in non-emergency situations such as when I asked them to do something and they didn't, I would ask, "Who am I?" and they would answer, "Mommy" and I would say, "who are you?" and they would answer "child" or "their name" and I would say, "What must you do?" and they child would say, "obey" and then I would say, "Ok then." and then they would do whatever it was that I had asked them to do. They knew the drill so well that as soon as I began to ask, "who am I?" they would either go ahead and do what I had ask, or say, "ok, ok, I'm doing it."
My kids are so amazing. They are now 21 (almost 22), 20, and 16 and they are such wonderful, remarkable, talented people. I have enjoyed every age and every stage of their lives and I count it the biggest priviledge of my life to have been their mother.
I hope that helps,
L.