With the issues you're having, I would think a re-format is in order.
I try to do a clean wipe and new install every 2 or 3 years.
One thing that I have done that you might want to consider is that
I divided my disk drive into two partitions. I put all my data on the
second partition. Therefore, I only need to re-install programs and
don't have to worry about backing up all my data files. (Which I sync
with another computer.
Depending on how full your disk is, you might be able to create a second
partition and move your data before wiping your main partition.