Phrase: "used to". Is that the correct spelling/usage ?

It looks and sound sunny but is grammatically correct.
for example "Jon and I went to the park" sounds weird but is perfect correct in terms of grammar

well "went" conveys motion... "used" as the past tense of "use" has nothing to do with a previous state of being...(if that made sense)

"i went to bed early" would mean that i went to bed early only on a particular night
whereas "I used to go to bed early." would mean that i go to bed not just for a particular night - it could be a week or a month

(i dont think this makes much sense) wait i'll ask my cousin - shes an english teacher-intern

it's correct.

i feel confirmed in this because a quick google search brought up several english grammar sites which discuss it (as a grammar geek i found it interesting - i never recognized exactly how to make a distinction between 'use to' and 'useD to') :
http://www.englishclub.com/grammar/verbs-m_used-to-do.htm
http://www.britishcouncil.org/learnenglish-central-grammar-used-to.htm
http://www.learnenglish.de/grammar/usedtotext.htm
and more....

While it is grammatically correct, it does have an awkward feel, and although I would probably use "used to" verbally, I would try to write around it, such as "Formerly, I went to bed early."

Likewise, many people use "suppose to" instead of (the correct usage) "supposed to". I think this is because the final "d" of the first word and initial "t" of the second blend into a single consonant sound when spoken.