Dear IslandGirl17:
Lying to him is definitely not a good solution. Since you are willing to accommodate him, at least partially, have a serious conversation with him: let him know that you are willing to accommodate him, at least partly. Then negotiate and come to agreed-upon accommodations: for example, you can decide in such negotiation, that before you commit to spending time with other guys, call him and let him know of the circumstance, get his feel about it and decide then, in conversation with him (or a few), following his input.
The two of you can come to some understandings, solutions that will work for you and for him. Get his input and talk back and forth. He will feel more powerful (not powerless and helpless as he does now, which causes him anxiety and excessive concern about you spending time with guys, and he is likely to relax) and you will be able to be truthful, to yourself and to him.
anita