Multiple queries regarding 4week old bab

Dear doctors, I have multiple queries regarding my 4week old baby girl. 1. She coughs up milk after and during every feed. Sometimes it is uncomfortable and comes through nose and mouth. Because of this I have to burp her atlwats 5-7 times after every feed and have to prop her up with support of an adult head pillow for most of the time.. atleast 40minutes after every feed. How long will this problem remain? 2. She also has constipated stool once or twice. She is on combination feed. How to relieve her of constipation? 3. She had looked spots in her stool twice. For this she was advised a formula with low lactose content and I was advises to cut off milk and milk products from my diet. When does this resolve? 4. Her face is full of acne type rashes - red bumps spread all over. It's there since last 4-5days. Is it concerning?