It's not okay to take someone else medications but well, Vyvanse is a stimulant in the category of amphetamines. Not suggested for anxiety but can be helpful for depression.
Wellbutrin could be a bit more suitable for you with less side-effects if dopamine and norepinephrine is a problem in your depression/anxiety. Depression often leads to anxiety so yeah maybe when you took Vyvanse you had euphoric effects similar to those with amphetamine ''speed''. The extra dopamine and norepinephrine you produce using this drug is contributing to the well-being feeling, focus and energy.
Ask your doctor if you could see if Wellbutrin could work for you then maybe suggest Vyvanse. It would be better if you try Wellbutrin first because it's less damaging for your health than amphetamine but can have similar effect but with less side-effects like increased BP and HT, tremors, lost of appetite etc.
Consider this -
Since Vyvanse is a stimulant/amphetamine long term use (especially for someone not prescribed) can lead to personality changes, aggressive behavior, homicidal/suicidal thoughts. Chronic users can experience Amphetamine Psychosis - resembles paranoid schizophrenia, delusions, hallucinations, and paranoia.
I second M4's suggestion - good advice.
Probably not the smartest thing to do taking a different med while taking your prescribed meds, but hey, if it works, id ask your doctor the next visit about switching. he may have you on the celexa for a reason.
I take 50 mg vyvanse, but for a month i was on wellbutrin. The wellbutrin cause be extremme levels of anxiety and made my vyvanse useless. Although, that may also be related to my bipolar disorder
Also, the euphoria associated with a first time vyvanse high will make you feel great. Ie no anxiety ect, but that doesnt last, vyvanse is not used for controlling anxiety and often exacerbates it instead in some people