Sex Drive and Relationships

I’m currently in a relationship I’ve been in for just over 1.5 years – I’m 29 and this is the longest relationship I’ve been in. I’m the type of person that likes to have change in my life (have proactively moved cities, to different teams at work, etc.) and I get the feeling of being bored/stuck in a rut pretty quickly. I love my boyfriend and our sex life has been great during the first year, but I’ve been feeling less and less excited about it. I’ve tried thought downloads and models, but I’m not getting to the core thoughts causing the problem. People typically say that physical intimacy in relationships ‘cools off’ in the first year or two, so maybe this is normal but I guess I should also be questioning what is “normal”. I’m sure 1.5 years looks very short in the context of many other peoples long terms relationships and marriages as well. Any insight into this would be great. Thanks!