I'm glad to hear it went well for you. It's perfectly normal to be worn out after OT as it's forcing your neurological system to do things it wants to resist. Feel free to tell your OT when you're feeling that way. Sometimes you may want to stop early. When my daughter did the brushing, she had to do it every 1.5 to 2 hours, so 3 to 5 times a days doesn't sound like a lot to me. If you think you'll forget, set a pleasant alarm in your cell phone--I find the harp sound not so offensive on my IPhone. Ask for a copy of the letter she sends your GP--you have every right to see it. The dx won't be SPD because it's not in the DSM, but it will be something that describes how your sensory symptoms are manifested. For my daughter, it was dyspraxia. The brushing was not helpful for my daughter, but she is not hypersensitive, and I've read it's more helpful for people with those symptoms. I've also read that, after the initial treatment, some people only do brushing when they're stressed or feel overloaded to calm down. The OT told us to stop immediately if the brushing made our daughter feel worse, so if it makes you feel more sensitive, you may want to call your OT to ask if you should continue.
It sounds like you're being very proactive about your treatment. You're doing great.