You are solving math problems when hashing, you might solve it on the first try or the 204385763th try. The hash rate you see is an average of how long its taking you, its not a real static number.
There is nothing wrong with your hash rate and there is literally no reason to try and mess with it as its functioning as intended.
Also you will NEVER make an identical amount of coins month to month, thats just not how mining works when it comes to difficulty. You might want to read up on what you are doing, things will make much more sense once you educate yourself.
Fantastic answer, good job you
it is a lot more than that but good answer nonetheless. The whole point is luck, you might find 5 shares in a minute with a gpu or 0 and if is more than 15 seconds(eth network block time) then anything you find after the block was found is stale, so your gpu has essentially 15 seconds to find a share.