Have you actually had a direct look at your credit score/record on a site such as Clearscore or Experian? You need to look at the details in case there’s something specific going on, and not keep guessing.

But one thing I will say is that a lot of the time when you apply for those current accounts, they do a hard credit search on you, and they generally advise not to apply for credit more than once every six months or so. If you apply for credit lots of times in a short space of time then it can exacerbate the problem. If you get rejected for something so you immediately apply for something else in case you have more luck there, you’re potentially making it worse for yourself.

If you join Clearscore (free to join, and you can sometimes sign up with Topcashback etc), not only can you see your score but they have a thing where they can help you find out first how likely you are to get approved for different things, so it helps you choose the one with the most successful outcome.