what drains my battery, I bought a new battery

copy and paste the link,try this.if you are sure the alternator,battery are good! How to Find a Parasitic Battery Drain - 9 Easy Steps www.wikihow.com › … › Car Batteries and Ignitions Last updated: Jun 01, 2015 · 1 min · 648,885 views

Don't discount the possibility of a failing alternator. I am sure you are driving in this 2 to 3 week span. So, a possible parasitic drain may not be the issue as the alternator should recharge the battery while driving. Since you seem to be slowly losing power even while driving, I have to assume alternator is not generating sufficient voltage all the time.