#soreness

I've been doing Pilates for like 5 years now and I still get so sore after every reformer class... is that normal? I mean I know it's a workout and all but sometimes I feel like I'm the only one who's dying the next day. My instructor says it's because I'm engaging my core properly but I'm not so sure. Do any of you have the same experience? I've been trying to increase my frequency to 3 times a week but if I'm gonna be sore all the time I don't know if it's worth it. Maybe I'm just not warming up or cooling down right??

i've been doing pilates for a while now and i still get really sore arms from the teaser. like my triceps are okay but my biceps and shoulders are killing me the next day. is this normal? am i doing it wrong or is it just a side effect of the exercise?