First, go with what Dave 225 suggests. Then, start thinking ...
Do you do a lot of stove-top boiling/cooking? Is your dryer being vented into a crawlspace or basement? Have you added another bathroom/shower? Is your humidifier set above 40% (assuming you have one)? Is your dehumidifier working properly (also assuming you have one)? Is the mold/mildew problem occurring around 'appliances / bathrooms / and such' where a lot of moisture is generated? Do you have a ventless gas / gas log / propane stove now?
Other than these 'thoughts', then you need to add a dehumidifier to get rid of the moisture. Sometimes, and I say sometimes, it's best to let the moisture into the main house, then get rid of it via a dehumidifier. If your home is tighter now due to new siding or roofing or insulation or vapor barriers being installed recently, then your 'problem' would be somewhat normal.
Those are my thoughts. My best to ya and hope this helps.
Jay J -Moderator
PS: PLEASE get back to me / us to let me / us know if any of the questions I / we have raised happen to 'trigger' something in your mind. From there, we can be more specific as to what you can consider doing to 'fix' the problem ... (Your Post will get buried right-quick. If it does, e-mail me directly or Post a new question refering to THIS post ...)