My mom did everything "perfectly" during her pregnancy, I was full term, and she breast fed me. SPD strongly negatively affects my life. Please don't blame yourself for something that such a high percentage of people have. In another time frame SPD would be a strength that would lead to an increased chance of survival. Which is why whatever gene combinations that can trigger it are so common.

On the friend thing. This is something you can help you child with. Tell them to befriend any other kids that seem to be outsiders or treated badly by the others. If they say no one else is, tell them they are blind (almost all kids get bullied or treated poorly at one time or another). Let your child know which days it is OK for them to invite a friend over to your house afterschool to hang out. You can provide activities, but a soft red ball that they can throw around outside is probably best to start with (have your child pick out the ball).

I got the bullies to leave me alone by making packs of all the freaks, geeks, and outsiders. We outnumbered the bullies by quite a bit and it gave us all safe people to hang out with.

It is especially important to befriend anyone that seems "creepy" or "annoying". They are the ones that need a friend the worst and have the hardest time obtaining friends. They are usually incredibly loyal and go out of their way to help you when you need it.

You can help your child by practicing with them ways to open up conversations. I tend to use jokes or silly statements. For example when standing in a line ask the person in front or behind you "so how many years have you been trapped in this line?" The statement is rediculous, but it tends to break the ice. I asked one kid if he was weird. When he said "yes", I told him that was good because I only befriended weird people.