It is, of course, up to you @Thedarksideofthemoon30. As others have said, and I’m sure you’re already aware, the risks of CVST are really very tiny. If you’ve ever taken the contraceptive pill, this carries a far far higher risk of blood clots than the AstraZeneca vaccine appears to. The side effects can be horrid, but anecdotally they’re generally milder with the second dose. Can I ask why you’ve already had it at your age op?
In the end, you have to make your own decisions based on your risk assessment. I would suggest, though, that you bear in mind that the newer variants in India and Brazil, seem to be affecting many more younger people adversely.
I’d also consider how it could affect you socially too. Will you be able to go to the cinema, theatre, gigs, etc, or will they all demand you have proof of two vaccines? I really hope not, but who knows. And then there’s the matter of foreign travel.
If, after thinking about all the above, you decide not to go ahead, I’d email your GP outlining your reasons and ask if there is any chance of you having a different second vaccine. They may say no, but nothing ventured .....
Good luck op.