There is nothing in Islam that connects 666 with the devil. The symbolism between 666 and the devil developed in history among Christians over time. There is a reasonably comprehensive discussion of this on Wikipedia: https://en.wikipedia.org/wiki/666_(number)
Still, it is unusual if you are seeing that everywhere. You should be sure it is not just observer bias. For instance, a person might see many numbers in one day but pay more attention to that number because it is meaningful and a little scary. If it is really showing up everywhere (for instance, several times a day in random places) and an objective observer would agree with it, that is definitely weird, although it's hard to say what that might mean.
Anyway, it seems like the underlying root of your question is whether you are just having bad luck of an ordinary kind, or whether there is something metaphysically unhealthy going on (for instance, the Qur'an discusses the evil eye).
Bad luck can indeed just sometimes be ordinary and due to decisions that don't work out (such as an investment or job that doesn't work out), the everyday travails of life (needing expensive dental work), or circumstances out of our control (such as how the coronavirus has affected the global economy).
(This is apart from genuinely bad choices which lead to bad results, but I'll assume that's not your case here.)
Sometimes what appears as bad luck is also a way that God guides us to do something else through fate. For instance, I try as hard as I can, but I can't get a job in a certain city or field, so I get a job in a different city or field, and this is par of my fate and a way of moving me on to something else. So, is it possible you are being guided towards something else?
And sometimes there are spiritual/metaphysical components, such as the evil eye, although that is less common. Anyway, if that is something you are concerned about, you could discuss it with a religious scholar who has knowledge of these things and who is trustworthy and see if they have any thoughts on your situation.
Also, don't forget, if you aren't doing so already, there are du'as and surahs you can recite to seek an increase in sustenance from Allah, for instance, Surah al-Waq'iah on Thursday nights. You can read more on duas.org.
Hope things get better for you!