Question about speech problem?

This is kind of a random question, and I honestly didn't know where to post it, so I decided to try here. I'll probably post this exact same question, word for word, in a few other sections, just out of hope of getting a few more answers. :)

Anyway, all my life I've had a slight speech impediment, and I thought I might as well try to get some thoughts about it on here. I've had problems with the "ch" "sh" and "j" sounds, along with any other words that use any variation of those sounds.

My question is about tongue placement during these sounds, particularly during the "sh" sound, as I can figure out the rest based on that. Where are the sides of the tongue and, most importantly, where is the tip of the tongue? What does the tongue do when making this sound? I feel absolutely ridiculous asking this, but I would really like to know, even if it doesn't cure my own problems with this.

My own tongue, during the "sh" sound, has the sides pressed up against the gums just inside the teeth. The tip of my tongue is behind my front teeth on the gums, which I know is wrong. I've gone to a specialist before and I was able to sound better, but tongue placement wasn't really clarified... And I know that's a key point to pronouncing such sounds correctly.

Thank you for reading; any help is greatly appreciated! :DD