Is it SPD?

My son is seven years old. He's very smart, very sweet, and a lot of fun. Most of the time. He is having some issues. He's been having them sporadically for several years, but it's gotten worse since we moved in with my boyfriend and his mother. My son likes them both very much, but it is understandably difficult to adjust to two new adults to answer to instead of just mom or just dad (his dad and I separated when he was 1.)

Since he was having these behavioral problems before the move, I doubt if the move is the sole cause. He says he loves it here, that he's glad we came, and is excited about our future with my boyfriend as a part of our family. His behavior is similar to what's described on this site, but I hesitate to jump right in and think he has SPD because he has no problems with sensory input. Although he is extremely ticklish, and a picky eater, (not nearly as picky as I was, though!) he has no other symptoms other than the behavior problems, which are mainly throwing fits and pooping his pants.

He throws fits when he has to do something he doesn't want to do, or when we tell him "no." I'll let him know it's going to happen several times in advance, to prepare him for it, but still, when it's time to change his activity he goes crazy. He'll yell, stomp his feet, and lie about things, saying I never told him he'd have to do it.

Today he even said that I told him I didn't like him anymore. Of course nothing is farther from the truth, but my patience is wearing thin. I thought maybe he was spoiled. He's an only child, being raised by single parents who live on opposite sides of the country, which doesn't even seem to bother him. He's used to major changes, has moved several times, and always adjusts very quickly and easily. Until now. Why? If it's SPD, why doesn't he have any other symptoms?

I don't have much money, no insurance, but if I need to take him to a doctor I will of course, but I just want to know if this could be an option. My son's dad is sure this is what it is, but how can this be when he doesn't have problems with anything to do with his senses?