Is this normal or do I just suck?

I tried looking online but couldn't find anything useful, basically today was my first time on zwift, I'm using a relatively cheap smart trainer (It's the tacx flow), I bought it specifically for zwift but didn't want to break the buck on something that I'm still not sure I was going to like.

When I started pedaling I felt like my avatar was moving waaaaay slower than what I would expect him to? I don't know it felt kind of underwhelming, I was moving at 143 watts and the resistance felt insane, my legs haven't hurted like this in a WHILE and my heart hasn't pumped liked this in a while either, the road was relatively flat (the map on the top right corner showed 3-5%) is this normal? am I really this weak but I didn't know it? I thought I was relatively used to riding a bike because I use it to move around town all the time.

I calibrated my trainer on the official tacx app, but I did enter my weight slightly above what I think it actually is (Because I haven't weighed myself in a while and thought it would be better If I just enter a higher weight).

Could the weight I entered be the problem? (90kgs compared to my actual weight which I guess might be around 84kgs?), or were my expectations just way too high?

Sorry if the post doesn't fit the sub or if I should've done more searching before posting but I don't see someone exactly having that same complaint.