sickness? I know y'all aren't Dr but what do you think it could be?

so my fiancé Monday morning his stomach felt blah and he had a headache, later that day he started aching and chilling and said he felt he was running a fever. he came home from work and went to bed. work up the next day and said he felt better. he went to work and he kept having diarrhea. stomach didn't hurt or anything just kept having to go to the bathroom. Now it is Thursday and he is still going to the bathroom 6 or so times a day. do you think he is still sick? if so do you think he would still be contagious?