I used to work in a clinic, and I have tried every edible under the sun. Like you I just get a slight change, but nothing significant?
I have just given up on it, it sucks when I watch whoever eat half of a xxx hash brownie, and then I eat the a whole one and they are in space and I am ready to smoke a blunt. And these are people that otherwise smoke me under the table any day, I just can't get it from edibles. I wish I could!