Hi Chris-tina, welcome to the forum! Yes, it is possible for anti-depressants to stop working, especially if you've been on them for a long time. I've had to change drugs twice because they lost their efficacy. It's best you talk with your doctor about it.
If you have to change drugs you will probably have to wean off the one you're on (reducing the dosage slowly) before you start on the new one. This is not fun. And it takes some time (a few weeks) before the new one kicks in, so it's not plesant to go through, but it is better in the long run than putting up with ineffective medication.
If you do have to do this, please follow your doc's instructions to the letter. Don't try to go off the current drug too quickly and certainly don't just stop taking it. That's dangerous.
Sorry to hear your drugs aren't working, I know how that feels. See you doctor as soon as you can - and if you are starting to sink really low, see them as a matter of urgency. If you start to feel suicidal or like harming yourself please go to hospital.
If you'd like to talk more about how you're feeling and what's going on for you, or even just chat, please feel free to post some more or join in anywhere you'd like on the forum. You are amongst friends and fellow travellers.
Best wishes
Kaz
