If you are writing your thesis, I assume that you are almost done or will be finishing up this year? If that is the case, I would recommend completing your major requirements for graduation.
If you are looking into english, journalism, or any other field, I would look into getting an *internship/volunteer/job shadow* in such a field. I do not think what you major in is all that important, if you enjoy doing it, and therefore, will try to get better at it, you will be all set.
What about a master's program in english or journalism? The entry requirements are usually not strict for a master's field. You may have to take a few extra courses, but they would be enjoyable courses as you said that you liked the field. You could also stick around another year and minor in something?
I would suggest talking to professors/advisors in your current major (and maybe even perspective majors if you were to do it all over again?) - I think you will be surprised about the various opportunities you can follow. You can talk to the career counselors at your college, they help people every day in your situation.
Have you looked into community college? A lot of the CC's around here offer post-grad diploma programs in journalism, corporate communications, publishing, that sort of thing. They generally don't care what kind of undergrad degree you have (so long as you have one), or even what your grades were like.
I sort of wished I'd chosen another major when getting my BS. Maybe accounting or nursing because at least I'd be more likely to have a job that pays well. But yeah there are some programs were you can get a masters degree in a different field like nursing, pharm tech things like that and you don't necessarily have to have your BS degree in that same field. You might want to try looking at some state school graduate programs to see what they have to offer. Every school will have different pre-reqs so you have to see if you have taken those clases, but if you are in the science field??? you probably have already taken them.
If it helps, my uncle studied engineering for his B.S in undergrad, graduated with honors only to realize he hated the field and never wanted to work in it. He decided he wanted to be a doctor, so he went to community college to get the coruses he needed and applied to med school. Long sotry short he got in and is now in residency. I know you said you didn't want to be a doctor but the message all is not lost, there's a way to make things right. Just focus.