Tongue tie means the frenulum (the string-like bit you can see under your tongue if you point it up to the roof of your mouth), is too short/tight to let the tongue move as freely as it should. Mild cases may cause no problems but sometimes it needs to be cut to free up the tongue.
Other causes to consider - cows milk allergy or intolerance. My DS4 (17months) has this, He was BF, but we noticed to started screaming/not sleeping/being clingy as soon as we started giving him milk to drink and solids (with cows milk/cheese in). We weaned him from BF onto Goats milk (all the supermarkets sell it, uht and fresh), it is much more like human milk than cows milk is (almost no one is allergic to goat milk, but MANY people have a problem with cows). If your baby is reacting to cows milk, you should see a very fast improvement in him (with in 3 or 4 days, with my son it was even faster), - so it's worth trying that :)
There are also special cow-free formulas, but TBH they are expensive, taste awful and are very artificial, so goat is probably a better choice.
My DS1 (Oxbridge!), was indeed a nightmare, very intense baby who required CONSTANT input and mental stimulation from birth (he still does :) )....... I'm sure the Dr was just trying to offer you a crumb of hope that all this crying is FOR something, but it was a stupid thing to say (as was the comment about colic not being real). But just in case! To increase the amount of mental stimulation (for any baby), change the babies view every 15 mins while they are awake by moving them or putting different toys or pictures in eye line, so they are always looking at something "new" - as a tiny baby I found DS1 got bored very quickly indeed, and was happy when kept very busy!