Your LSB is ~ 15.7 uV. Look at supply rails with DSO on infinite persistence
to get a handle on pk-pk noise.
The following may help -
Use bypass the reference option.
What is in the signal path between sensor and A/D ? Lot of CM in design,
if so are you using differential conversion ?
Look at CM range, see below.
PSOC DelSig CM Range.jpg 97.0 K