Learn English – Question about “very” vs. “too” – with and without “much”

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).}