How do I do it correctly?

I have mild adhd, I am on a prescription for 40 mg of medikinet. I take it orally every single day. I feel nothing everyday. So yesterday I took a risk and took 3 at once. Felt nothing. But I somehow managed to accidentally pull an all nighter? Previously I had Tried crushing it up and snorting it but I didn’t crush it fine enough and I spilled a lot of it so it didn’t surprise me when I didn’t feel anything. People say post 120 mg you can overdose? I was on 120 mg and felt nothing. It’s not like I’m heavy weight btw. M15, 5,4 43kg. I know. Like am I doing something wrong what the fuck? I’m so confused, I’m thinking of changing to concerta instead but idk man. Can one of you tell me what’s happening and how to fix it. I just want to try it.