As I understand it, while the odd dialect does trill the R (the northern extremities, in particular), the sound should be more of a 'flapped' R. Try pronouncing the word 'water' as quickly as possible, and listen to the sound the T makes. (Depending on your accent, but probably) It's not actually a 't' (or 'd') sound, but it is a Swedish R sound. It's the same as the R in the Spanish word 'tres', or the initial consonant in the Japanese ら. To me, the Swedish R sounds like the monomer that makes the trilled R, but I'm not sure of the actual, linguistic accuracy of that.
I'm not a native Swedish speaker, but what I've learned over the years is that "jag" is properly pronounced "yahg", but that much of the time (probably most of the time) people shorten it to just "yah". I wonder if pronouncing it fully ("yahg") seems weird or overly formal or overly precise in casual conversation.
It can also mean to be drinking alcohol, just like in english.
"Jag dricker inte" = (literally) I don't drink = I don't drink alcohol
You never say that if you mean drinking something else than alcohol; instead you specify by naming the beverage (like tea or milk.) If you don't mention what kind of bevarage you're drinking, people will assume it's alcohol you're talking about.