It's rotational based on record and Strength of Schedule. In your example (before trades) KC and Jacksonville finished tied for the worst record in the league but KC faced a weaker group of teams, so they pick #1 in the first, then rotate to #2 in the 2nd, back to #1 in the 3rd, etc...swapping with Jax each round.
When there are multiple teams involved, say four teams that finished 5-11 and are slotted for picks 7-10, it's just a longer rotation. The worst SOS team will get pick #7 in the first round, then rotate to pick #10 in round two, #9 in round three, #8 in round four, and back to #7 in round five, and so on.
Checking ESPN, you guys finished at 8-8 with Pittsburgh last season, so your teams picks would have been moving back and forth one spot each round pre-trades.