Rsv, common cold, help!

Baby is 5 months and has been very congested the last two days and his temperature is 99.9. He is coughing, weezing, breathing is difficult when hes sleeping it becomes fast and heavy and loud. He wont sleep on his back now and breathing seems more heavier on his stomach but I cant keep him on his back. When he is awake he mostly seems in good spirits breaths good but still very congested sneezing coughing and gets irritable rubs his nose. He is very talkative wants to play, eats his normal amount as if hes not that sick but then for nap and night time it gets completely bad. We've been doing saline drops with suction bul, humidifiers, and warm baths. Should I take him in to be seen? Common cold, rsv? FTM and worried! It's just weird hes mostly fine and so happy but then when nap and night time come around he seems really sick again.