Need serious help (never filed taxes before)

I’ve been buying and selling crypto for a few years but never made any actual gains. Fast forward to 2020/21 (I believe) when the market exploded I made a significant profit but by the end of the bull market I believe my profit was still under the Capital gains allowance (£12300) but now, I’m not even sure about that (I’ve used a few different exchanges, some required KYC and others didn’t)I used Koinly to track my profit and losses but after doing so many transactions (swapped between different crypto among exchanges) I may have gone past the allowance. I haven’t touched crypto in the following years and never filed taxes before. Now I got back into and done some swaps here and there and got some profits. I was so stupid that I didn’t even check that the allowance for the year 2023/24 has gone down to £6k (I made a couple of thousands pound in profit so I’m definitely have to declare that). To add more trouble to the situation I never registered for self assessment and we’re past the deadline. I’ve been freaking out for the past week and reading stories of people that eventually got caught not paying their taxes made me worry even more. I’m currently looking for an accountant but I don’t even know where to begin. I’ve been struggling with anxiety and depression for the past years and this made it worse (I know it’s all my fault, I’m not denying that). What should I do? I do have some money set aside in my savings but what if I will end up more than I can afford? I do have a full time job and pay income tax. I know I should have sorted my situation before and regret not doing it and now I feel like I might receive a letter or phone from HMRC at any point. Please any help would be appreciated. Sorry for the long message, but I’m seriously freaking out.