Teething or illness?

Hi all, My LO is just over 5 months and from the start of this week he’s had very runny yellow poo he’s formula fed. We thought it might be rota virus as we don’t anti bac wipe his changing mats often. So we got new ones and a new steriliser and bottles and we noticed a difference that his poos has now become more loose- he can constipation for a couple of days afterwards. Today I checked his temp twice as he seemed warm to me and it was 37.2. We only have one that goes under the arm. What I’m unsure of is it a virus or teething? He has flushed cheeks, always biting everything in sight lots of fussiness and dribble, wanting more contact naps? Phoned doctor this week and she doesn’t think the toys as such would be the biggest issue as I try and sterilise them however he’s always putting them in his mouth and unsure how often to do it? I’m wondering if it was more the changing mats maybe? Any advice? Just worried