My girl wants more love than i can give - what can i do?

we only see each other at weekends, and have missed each other so much we spend hours and hours in bed catching up. Positive is that i lose around a Kilo each time - negative is that on Sundays we always plan a trip in the city or countryside, but after breakfast we always land in bed again. just cant resist. This has been going on for 8 months now and my problem is that on mondays i am exhausted - completely tired and unable top concentrate. We always say we will cut down, but one of us is always weak. please help! (only serious answers please)