I just started taking Wellbutrin 150mg XL prescribed by my doctor 18 days ago for MDD . I was taking

Hi, Falcon!
It's uncomfortable but it's the roller coaster of your metabolism adjusting to the medication. You may find you also have better mood days and then have a few bad ones for the first few weeks.
Your side effects seem to be hanging on a little longer than usual so I'd let your doctor know.
It may be a matter of just giving it a little more time or maybe a temporary lower dose until you're better adjusted?
Just for the record, I've been on many very effective antidepressants with no significant side effects but the standard classes always caused me to have manic episodes (I'm Bipolar). I was switched to bupropion (Wellbutrin) because it's an atypical antidepressant that often has less, if any, side effects for most people. I've taken it now for over 4 years and it's been a true game changer for me.
Best regards and I hope you'll be feeling better quickly now.
Wildcat

All I can say is that I have tried pretty much every class of antidepressant and had serious side effects with all of them, so I will never take another one again. Now, I have been taking tadalafil a couple years for ED, and I have been very happy with it.