ANSWER:
You were totally wrong for missing salah again, even if you were sick you should have prayed sitting down, if you couldn’t stand or lying down if you couldn’t even sit!
There’s no need for renewing the Shahada but you must repent sincerely to Allah, with deep remorse as your iman seems to be weak and you miss prayers at the drop of an hat. Do a lot of extra night prayers and other good deeds like charity etc to try to compensate for missing prayers intentionally.