The first version "use to" is a verb form which means that there was something that I did in the past, but I now no longer do.
The second version "used to" is an adjective form which means that I am accustomed to, or adjusted to something.
Where's the problem?
Well, there are a two main things to think about here:
The first one is that because the first form is always talking about things in the past, it normally (but not always) takes the past construction: "used to" which looks exactly like the second version....see the problem here?
The second is that the 'd' sound in "used to" is very weak, so when you hear a native say it, it does tend to sound exactly like the first version: "use to"... (great...uh?)
What can you do?
We apply the construction "use to + verb" when talking about things that we did, but no longer do. Because we're talking about the past, the form will take an -ed ending and look like this:
"I used to live in London." (I don't live in London any more.)
"I used to go swimming every day." (Now I do something else).
We will see "use to" (the base form) when the past is described by another verb, like here:
- "David didn't use to like classical music." (now, apparently, he does).
- "Did your mother use to work at the University?" (we aren't sure).
On the other hand, we use the construction "to be + used to" when we are talking about something that we are accustomed to. Sentences will look like this:
- "I'm used to my boss doing this: he always changes his mind."
(I am accustomed to this behaviour).
- "Don't worry about the noise, my baby is used to it."
(Her baby is adjusted to noisy conditions).
And sometimes you'll see both versions together in the same sentence:
- "I used to live in London, so I'm used to the noise."
(I no longer live in London and I'm accustomed to the noise).