Here's a reply for you...
Selecting Weekly backup will give you monthly as well unless you choose not to retain them below.)
Sounds like you've not configured it as you'd like. And if you were to check out this link,
CPU/Memory/MySQL Usage you might see that gzip is whats causing server load during backup as it compresses your files.
Lot's to learn using cPanel. And lots of good Info on these forums. Most problems you'll come across, someones been there before you and there's a thread here somewhere that'll help you understand more about them.
A great place to start, is
here.