firstly, you should maybe put in a little less effort so that you don't overwork yourself and/or your body. go at a pace that feels right but not overly strenuous for you. secondly, i'm sorry they're coming across that way, that sucks. there's a high chance though that they just don't know you yet and/or aren't the warmest people in general. it's likely nothing that YOU did. also, sometimes it can be the work environment that causes coworkers to react poorly to one another, because they're stressed out. it's not okay if they are taking that out on you, but they may not be and you may be being a little hard on yourself by saying you're not doing enough for them to be happy. try to remember to focus on your happiness too, and know that how they're treating you is most likely not your fault!!