All of these sentences are grammatically correct, but you won't hear the last one very often, and probably never* encounter the first one. They mean different things.
☼¹ I feel sleepy very much.
I feel sleepy too much.
These are possible ways of referring to how often someone feels sleepy. That is, how frequently. There is some of the statement left off, which would make these sentences:
☼ I feel sleepy very much [of the time].
I feel sleepy too much [of the time].
When someone says “too” they are suggesting an excess beyond an acceptable level. In this case, the acceptable level would be feeling sleepy at regular times or just at the end of the day. The following dialog is possible:
“Why don’t you like taking that medication?”
“I feel sleepy too much (of the time).”
“Too” is also used in one of your other examples:
I feel too sleepy.
Again, someone saying this is implying a tolerance limit that has been exceeded. Someone might make this declaration as they left the company of a group late at night, and the implication would be that they are too sleepy to continue doing what they are doing. More likely you’d hear it in situations like this:
“Why don’t you go with us to the nightclub?”
“I’m too sleepy.”
Most people would say that they are sleepy (not that they “feel” sleepy) unless they are describing something that is similar to sleepiness, especially something externally imposed. c.f.:
“Is the nitrous oxide flowing?”
“Yes. I feel very sleepy.”
More likely people who are very sleepy in normal situations will just say “I am very sleepy.”
1 ☼ = descriptively ungrammatical (violates practice, but not rules).
The two things mean something rather different. "Too little, too late" indicates there was two shortfalls, "a little too late" indicates there was one shortfall.
Effort on your homework was too little and too late.
Here the speaker is indicating both that there was too little effort on the homework and that that effort was applied too late.
Effort on your homework was a little too late.
Here the speaker indicates only that the effort was too late, and the lateness was only a little lateness. Nothing is said of the size of the effort, only its tardiness.
Best Answer
"So much" in this example is being used to denote that you have a lot of work to do, but it can also imply a specified amount.
For example:
This is the same meaning of the word but is being used to show that you have a limit to what you can do.
"Too much" in your example has a different meaning, not simply that you have a lot, but that the amount you have is excessive.
Consider this example:
This means that one person cannot drink that amount.
When used in your example:
This implies one of two meanings, either that (1) it is not possible to complete the amount of work you have; or, if said in answer to a question such as "can you do something for me?", that (2) the amount of work you have is does not allow you time to do this new task being asked of you.