Dear Friend....
It sounds like you are very insecure in your relationship with your
husband because of your jealousy and fear about his request.  Every
couple needs boundaries to protect their relationship without
imprisoning them in it but allowing each spouse enough freedom for trust and personal development. 
I would suggest that you read Loving Your Marriage Enough to Protect It by Jerry Jenkins found our resources page.  This book will help you and your husband discuss the reasonable boundaries you can agree to put into practice when you are each in situations where you have contact with the opposite sex, ie., work, church, socials, recreation, etc.
Then, I would suggest that you come up with your own requests which will make you feel more secure in your marriage but not make your husband feel inadequate to meet your needs and guilty when he wants time to himself.
You both need to care enough about your relationship to tell each other
where you are going, with whom and for how long.  Personally, my husband and I have always told each other where we are going and what time we will be home. 
If my husband told me he was going to a bar, I would be very concerned about that.  Why?  Because if he was sitting in a bar he might meet other women and because he would be drinking alcohol he would
be tempted him to do things he might not otherwise do. Thankfully, my
spouse does not do this because he is a Christian and he desires to please God.
If your spouse does not want to talk about where he is going and where
he can be found in case of emergency, then, you have something to worry about.  Anytime a spouse begins to hide his/her wherabouts and
activities there is reason to be suspect.  Openness and honesty are
highlights of a healthy relationship and the foundation of trust
necessary for any growing marriage.
You can come up with some suggestions about activities you can do
together without actually being together, also.  Such as working out
at a health club or going to the library to read.  Or go to a museum
and spend part of the time together and part of it viewing different
exhibits you personally enjoy, then, meet or coffee or lunch.   Or go to a shopping mall and shop in different stores meeting later on.
Maybe you need to build some friendships together as well.  Getting together with other couples is a very enjoyable and healthy thing to do.
Explore with your husband what makes him feel like he needs time alone.  Let him tell you what might be bothering him about your relationship.  He may be feeling trapped for some reason.  Evaluate the last 3-6 months.  What happens when he is off work?  Do the two of you constantly do everything together? When he is engaged in different activities are they always responsibilities around the house or only things which you like to do?  Does he ever have time for his own personal hobbies or to go fishing and be outdoors?
You may have different personalities also.  If he is an introvert he will 
need more time alone and when you are in the house together he may feel that he doesn't have time to concentrate on his interests.  So it might be wise to let him have his space at home too, so he can read, or do computer work, etc.
I hope this is helpful for you.  If you have a good relationship with
your husband then I don't think you have to worry about anything.
Actually, worrying never accomplishes anything good anyway.  Read the articles on anxiety and faith to help you trust God more for your relationship with your husband.
If your spouse is not a drinker or a gambler, etc., then be grateful.
Build your own self-esteem so that you are not overly dependent on your husband's attention.  Read  The Search for Significance by Robert McGee found our resources page. 
Explore with someone... a confidante, mentor or counselor what has happened in the past to cause you to be so jealous and feel so insecure.     God bless you!  May I have your permission to reprint your question anonymously?  Thank you!      Lynette Hoy, NCC, LCPC