The phenomenon you have observed is "glide absorption". The glide "y" is absorbed into the preceding consonant. (I have never heard it in "I feel good, yeah", but it applies to all your other examples. Be careful. Some of them are the "j" sound, not "ch".) The following may be helpful. I'll take a look at your responses if you care to do the suggested exercises.

Type 1. t + y = t + sh = ch

When a "t" at the end of one word comes in contact with a "y" in the following word, the combination creates the sound . The most frequent "y"-words that are seen
in this context are "you", "your", "yourself", and "yours". The word "year" also can be seen in this context.

"Won't you help me?" > Won choo help me?
"At your service!" > A cher service!
"last year" > lass cheer

Exercise: Transcribe the portions within .
"!", "I know care.", "Did I ?",
"They'll ", "", ""

Type 2. d + y = d + zh = j

When a "d" at the end of one word comes in contact with a "y" in the following word, the combination creates the sound .

"Could you pass the salt?" > cou joo pass the salt?
"Did they find you?" did they fine joo?

Exercise: Transcribe within .
" hear me?", "We'll to the list.",
"?", " sleep?"

In brief, Type 3 is s + y = sh and Type 4 is z + y = zh

Glide absorption between words is not required but most people use it all the time. It is a natural phenomenon in spoken English. In my opinion, you will never speak authentic English unless you master glide absorption.

Note that within a word (as opposed to between two words), glide absorption is almost always required:

nature = nate yure The "t" joins with the "y" to form "ch": na chure. (Type 1)
pleasure = plez yure The "z" joins with the "y" to form "zh": ple zhure (Type 4)

Note that the "u" is pronounced with a glide, so is effectively "yoo".