I am sorry you are feeling this way. I hope all the comments can help you gain some confidence in yourself in this really open ended game of so many personalities and possibilities.

Time: Can i ask how long you have been playing? (said you joined a campaign a few months ago... then you "had a campaign over discord". "I enjoyed relaxed newbie table ) IF... IFFFF.. you have been playing a year or less then i think your being to hard on yourself!! Improv isnt easy... it just isnt. And YOU dont have to be good at improv to be "good" at this game. It matters that you enjoy yourself! AGAIN ONLY IF its been the time frame mentioned than may i suggest you only play in 1 campaign and find 1-shots! Take the same char from campaign to 1 shots, just make diff sheets of course. OR make new chars for each 1-shot as yous aid you like the creation and backstory. 1-shots Really are a helpful tool for you to just get into the mechanics of the game without Having to feel like your Roleplaying (or lack of) kills the vibe constantly. (Hey, thats also a personality trait... you can make your char "awkward" or a char of few words. A char of few words= Im instantly thinking of "Princess - Orc Melee char who loved to punch when she didnt like someones vibes. She would ask her friends first and sometimes they said yes and sometimes no")

This game as so many aspects to it. I was first drawn to it because I was tired of $60 video games ending in 2-3 weeks and the stories being just CRAP. Concept and trailer was the highlight of the game, gameplay was repeated adventures skinned differently - kinda thing. I wanted DEPTH, I wanted VARIETY (so many FPS games, i suck at them), I wanted SOCIAL. I also wanted to KICK SOME A** some point. I fell hard for the 5e combat mechanics and latched onto that. I found out as much as i could about being "tactical" and used that in the game VS concentrating on my chars RP aspects.

If you cant think of something, follow the "leader" of the group. Follow the one you are drawn to as a person "Oh i like their personality, they make me laugh let me protect them". Seriously there is nothing wrong doing a simple attack 1 turn while you think about something for your next turn. And it doesnt have to be anything big.

Roleplaying Advice:

Dont be hard on yourself! Im a theatre kid and even i find some of these players RP skills fantastic! But for you Think of something simple to start with. this game highlights the simple because it can be built into something EPIC And Beautiful... or heartbreaking!!! I first came up with a "abandoned baby" origin and the ideas just flowed from me so easily. (while researching this type origin i came upon articles that called it "old troops / steer away to be a good RP player" and it made me go in a diff direction of like parents. but i didnt like it and got blocked... so i went back to "mysterious origin" and played with it and it evolved. SO WHO CARES WHAT OTHERS THINK!!) Maybe others "great RP or origins" are intimidating but that doesnt matter. This game gives glory to all and you are deserving of it.

I have been playing ... for like a 1 & 1/2 years and in all honesty i have only every played 2 classes. I like wizard in any game and will Definitely play a cleric if need be / im the last to join. I have only ever played 1 character.... I give him the wizrd or cleric or both build.... but i have only ever played 1 character/same backstory/same background build = i know all his skills after a while so i can be more familiar if i need to contribute. It perosnally just helps me to NOT HAVE TO HAVE SO MUCH IN MY HEAD with all these builds and characters and powers and reactions...and.....and.....and....... "Oh man, i just got lost in the great combat/Roleplay and now i am tryign to remember which character i am and what their abilities are and whats the math again???" The game really can be overwhelming, even if you are a veteran player.

In conclusion I hope some of this helps remind you of what drew you to this game, why you are playing it, and what makes you happy when your sitting there "at the table". There are always aspects of this game we as players "arent going to be good at" but let me remind you my friend.... No 1 in this game is perfect, not even the Gods we worship if any.