Great Relationship...Bad Sex

Hey guys. Are any of you in a relationship that is perfect in all aspects. Best friend, great connection, financially stable, have kids together, but the sex just isn’t there? It’s like I can’t allow myself to get comfortable so I never enjoy it. There are no sensual parts to it, it’s just sex, no love. How do I fix this? I love my partner, but this aspect sucks and definitely affects the relationship from my end!