How much did u gain I'm 1st trimester

I'm 12 weeks Sunday I'm at the doc n weighed in at 122 now I'm 128 . I'm feeling very insecure I kno people are like shut up but I wAnt to be healthy n baby healthy to , I don't work out maybe o should maybe do treadmill 2-3 times aweek for 20 mins , any advice ? This is me by the way . I'm feeling pretty amazing until I saw that weight gain , someone said your not supposed to gain anything at this point , ladies just trying to feel better .  Lol my make self jeans looser lol