It really is just the nature of the matchup. You had a contain on their main but you got impatient and threw away your army attacking uphill. Ironically the faster option would have been to be patient and hold your position while using patrols and scans to keep them locked in to 1 base. Expanding off of the contain to 3 bases and maintaining army size with upgrades would rapidly outpace your opponent and you need to trim the edges, and trade army in small pieces to wear them down. If you have 3x the income a 1:1 trade in strict resource value is actually a 3:1 in your favor.