You have a known side effect from an rx medication. It is a medication you presumably need and if you feel you don't discuss it with your prescribing doctor or get second or third opinions from other doctors specializing in the relative field.
You have a pharmacological problem. It would be unethical of any of us here to tell you to stop taking an rx medication. The only intelligent path forward is talking to your MD about the problems so that they can decide if altering your rx regimen can be done safely within the context of your situation to address this side effect that is clearly disconcerting for you.
Taking hormones that your MD did not prescribe, is frankly a dangerous and foolish idea. Not only is it unlikely to actually help your problem as the suppression of libido from lithium is unrelated to testosterone....................... but it could actually make the underlying condition you're using lithium for worse or imbalance you in other ways.
This discussion doesn't have to be about just adding more and more rx agents. You can discuss the possibility of a future without Lithium for you if you're doing well on something else. You say you've been prescribed Wellbutrin and if it helps you in general, discuss with your MD the possibility of using that in lieu of the Lithium if symptoms are under control and you're feeling good.