Is my period "long" enough?

I'm 18 years old and I recently have been having shorter periods! I used to have a 7 day period and this is when I ate all meats I guess I should add lol now that I only eat chicken and some times fish and I've been working out my periods are 3 - 4 days usually ending on the 3rd day with little to no blood that day. Is this normal? Or should I go see my doctor