Low level DnD is just very swingy, because you have so few hit points. It is very easy to kill and get killed in a single attack, in a way it is not anymore at higher levels.
Low level dnd is always the most deadly (I have seen some statistics on this in the Lost mines of Phandelver, even. Most TPKs are in the first fight lol)
Your stats are fine, I think you really were just unlucky.
For the future, I would advice realizing how squishy you are, and acting accordingly.
Like in real life, you will not survive being stabbed. So try to position yourself before the fight, sneak up on enemies and so on, instead of rushing in.
The Intellect Devourers really are scary and I too died to them in my first run. After that, the game gets easier, because you (and the enemy) have more HP relative to the damage enemies (and you) can put out.
