1999 Chevy Blazer 4 cyl Four Wheel Drive Automatic 96000 miles

I have a 99 Chevy Blazer that has multiple starting problems. for the past couple years, if the temp is below 32degrees outside vehicle wont start, I learned to keep it in the garage for the most part. Recently i have a bigger problem, if i don't use it within 24 hours it doesn't want to start. I try and try, hear the fuel pump enage, battery was tested and fine, but it tries to turn over, but it doesn't fully start, sometimes after many many tries it will, other times, if i put a battery charger on it and turn to start position, it starts right up. I have had the battery tested and it was fine, even replaced battery and still same problem.