My Dog Didn't Eat Today...lays Around Won't Go Outside, Every

My dog didn't eat today...lays around won't go outside, every once in awhile it looks like he is trying to throw up but can't, gags and hawks, and now I checked and his ears and extremities are cold...I think he ate something bad...we live in the country and he was chewing/ eating some manure that fell off a truck...really concentrated stuff, what can I do to make him throw up or what should I do...I tried to get him up to go outside to pee before bed and he didn't ...