A she was entering a new developmental stage my daughter would start doing something she never did before (usually not new and good things ;-) At about 3 months she decided it was me or no one, too!
Luckily I caught on quick and what really helped was giving her even more Mama time until she rode out the changes going on in her little body and brain.
Instead of tummy time try holding her higher up against your shoulder and dancing to music in the living room. My daughter LOVED it and she held up her head and sat up on her own way ahead of schedule. Just start gently and have fun! It's kind of like baby Pilates - good core work for the both of you!
I know it's more difficult when you work but giving her more body contact with you will assure her that her Mommy will be there. It's hard work being a baby! Instead of her swing, put her in a front carrier and take her for a swing on a real swing.
It may seem like so much to handle on your own since your husband is gone and you're working - but you'll not only be making a lasting impression on your daughter that when the going gets tough you will be there for her, and dancing and swinging and being close to your daughter and her sweet baby smell really will make your day better!
When she seems to be through this developmental rough spot, she'll be on to another so be prepared ;-)
I agree with the others that she probably will freak when your husband comes home (if she is still not wanting to be held by other people.) She doesn't know him yet, but she will, and soon enough her world will revolve around him and you'll be longing for these days of Velcro Baby!
But if this is his first child, he'll probably be equally freaked (and thrilled). Give him a heads up and he may welcome the "out" initially. Spend time cuddling on the couch with your daughter AND your husband and she'll be seeing the both of you as her family - that loves her SO much!
Good luck! Boy, I miss the baby days... =)