There were a lot of valuable tips already (especially the needle tip / needle body thing!). But I am worried there could be another problem since it seems you are learning from videos only, not with a person:
does your yarn fit your needles? a lot of self taught beginners start with just any yarn and needles... then the result is bulky or tight knitting...
for a good result I advice to take a yarn with some give (a yarn that stretches a lot or little when you pull it). Then the yarn will be a little more forgiving to tight knitting. Cotton often has no give at all, so it makes it tight - but it is often colorful and cheap and therefore is appealing to knitters :D
the other thing is: if your yarn is too thick for your needles (or very thick in comparison) then there is a lot of material to master... that turns very thick...
the reason is the following:
if you see the needle: it is round, so the measure around is twice the radius (or once the diameter) times pi. you can just find out how much yarn you use for a stitch.
on a needle with 5 milimeter diameter there is an approximate way of 15 mm around the needle...
now for getting a stitch worked, you need to get the yarn twice throught that loop. The size of the loop depends on the needle. the size of the yarn has to match now.
if the 15 mm loop has to go around yarn that is 6 milimeters thick, for example: then there is 12 mm yarn in between - and that is very tight.
the good thing: yarns do lable - mostly - what size needle is recommended.
please do yourself the favor and stick with that recomendation until you know just all about yarn and knitting - or at least a bit more
do you have the chance to make a video of you knitting? then we could comment on the actual process.