I go to crossfit everyday of the week except on sunday (because there is no class on sunday). I weigh 220 lbs and considered over weight, so I struggle a lot to complete the workout. I am not sure, if resting couple of days would help. I tried resting this week by not going yesterday and today, but I feel more tired than days I workout. what should I do?
You would be much better off lifting three days a week (full body workouts using compound lifts) and walking (perhaps briskly) for one or two other days of the week. If weight loss is your goal I would also suggest looking at your diet.
From what you're describing with you and CrossFit it sounds like your body cannot recover from what you are doing there.
Definitely agree with user9941 about diet -- as cliched as it is, "you can't out train a bad diet", applies to the majority of people.
Having said that, it's really an individual answer and there isn't one right answer for everyone regarding how many days they can do CrossFit. You need to listen to your body. Are you getting 8+ hours of sleep every night? Is your nutrition dialed in? Are you in your 20s, 30s, 40s, or older? What intensity level are you exerting at each workout?
If you are 50+, getting 4 hours of sleep per night, eating a standard American diet (and/or trying to starve yourself to lose weight), and are ending each CrossFit workout having pushed yourself to the limit (i.e. laying on the floor in a puddle of sweat trying not to throw up and get an exercise induced headache), then 6 days per week is way too much.
If you're in your 20s, getting 9+ hours of sleep per night, eating clean (with plenty of good pre and post workout carbs), and you're only going all out for 2-3 of the workouts, and really focusing on skill progressions/strength/form on the other 3-4, then you're probably going to do great with 6 days per week (and could potentially handle even more).
Assuming you're somewhere in between, you have to listen to your own body about how you're recovering. If you feel beat up, then you probably are, and you should scale back.
Talk to you coach(es) and see what they think.