Melt 1 bag chocolate chips in the microwave (15 seconds, stir, repeat until melted smooth).
Spread chocolate in bottom of a 9x9 pan. Layer pretzels to cover the chocolate. Let chocolate harden.
Pour 2 cans of sweetened condensed milk into a saucepan over medium-low heat. Stir constantly until it thickens (20-25 minutes). Remove from heat and spread over pretzels and chocolate. Let cool.
Melt 1 more bag of chocolate chips. Spread on top of caramel layer. Let chocolate harden.