I’m worried about my kitten

For about 4 days now my little kitten Tom has been very sick. this is a huge problem as i have just been laid off my job and can’t afford to take him to a┬ávet. about 3 weeks ago i bought a hartz collar because he’s indoor/outdoor. I can’t say for sure if this is what is making him sick, but i had a strong feeling about it before even seeing this website. he’s vomiting has no appetite, and sleeps all the time (which is not like him) He did finally eat a little today (i took his collar off yesterday) any recomendations PLEASE!