well but this may be somewhat more correct.
a) wanted to (do something) = (하고) 싶었다. 싶었어요. note that -었 is the past tense morpheme, and -요 is for honorific form used when meeting older people. So basically when meeting the older interlocutor, and wanna say that you wanted to eat apple in Korean, "사과를 먹고 싶었어요."
b) regret something you've not done and want to express this emotion = 싶었다. 싶었어요. the same expression, but slightly different shade of meaning. It is commonly used in an act of speaking his/her thoughts aloud when regretted.
i. e."정말 착하게 살고 싶었어요... (하지만 착하게 살지 못했어요)"
= I should have led a good life...
in short, a) wanting, b) regretting. As Joshua said, it desperately depens on the situation and context.