Have you been taking your folic Acid tablets 24 hours after your MTX dose, most important helps with Vitamin B levels that the MTX wipes out.
I have been on MTX for 10 years now, am on 35mg once a week, as well as another immunine suppressor, so always watch for infections. Get on top if possible chesty issues fairly quickly, Vit C and or multi vitamins for a start, and then if I have to see the GP, he gives me antibiotics especially if I am running a temp.
Thank goodness I don't have a lot of problems, even through a double hip replacement scared me a little that I might get an infection but hospital extra careful and I also used common sense.
Didn't take my MTX the same week of my surgery, surgeon approved, and because I am on MTX you are cyto toxic, dressed in bright purple, all dressings bagged up in purple bags, every time nurses had to deal with me dressed in purple aprons, purple sheets on bed, purple gowns rather than my own.
Caused a little anxiety as to why I was being treated differently to others in the ward, but when I explained why and also explained it couldn't affect them, but their germs could kill me, nurses also backed up my explaination even though it was a little simplistic.
I do not treat myself as though I am going to die from the first infection that hits me, go swimming in the local heated pool, nobody has told me not to, been doing it for years now, helps with exercises post hip replacemnts, do my own shopping, nothing has more nasty bugs than supermarket trolleys ughhhh, generally try to be sensible, wash hands, don't rub eyes with unwashed hands, general sensible clean rules, ceratinly don't go crazy with cleaning, you do need some bacteria.