I was put on Zoloft (Sertraline) about 6 years ago for the first time. I started at 25mg and it seemed to not work much, so we heightened it to 50mg, and eventually tried 100mg, but it made me feel super-dizzy and light-headed, so then we tried 75mg and it did good for about 5 years! I lived my life feeling great and completely normal, and then after around the 5-year mark, we decided to try to lower it to 50mg. It did me pretty good for almost a year, but about a month ago, my anxiety returned worse than ever. So I went to my doctor about 3 weeks ago, and we upped it to 75mg again. I started feeling a little better within around a week/week and a half. I still get really nervous around the evening/night, and I'm not sure why, but I decided to make another appointment with my doctor in a couple weeks to see if we could try 100mg again (considering I was just about 11 when we tried it before, my body might can handle it now).
As far as side-effects go, it very-well can make you nauseous and it made me have pretty much no appetite for a while. It can cause different symptoms for different people, and they usually subside within the first 4-6 weeks as I've experienced.
From my experience, Zoloft is a really good SSRI that has helped me immensely, and I hope I can get it to continue to do so.
If you can tough it out through the side-effects, I'm sure within about a month or two, you will start feeling lots better, and if not, it may not be the SSRI for you. But you are on a very low dose right now, so before calling it quits with Zoloft, I recommend you (with your doctor's permission) slowly increase the dosage as your doctor says for you to.
Just try to be strong and push through, I know it can be one of the worst things on earth it seems, but with SSRI's, a good therapist, and the willpower to overcome this, many many people have gone on to have happy, normal, great lives. :)