*Loan,banking and credit>>>mortgage loan

If I have a mortgage can I use the house as collateral for a personal loan if I have a mortgage?

Yes but, as a rule, the mortgage plus your new loan must not exceed the value of your home. If the total of your loans exceeds 80% of the value, the lender will almost certainly insist on mortgage insurance. With this, you pay the premiums but the mortgage company gets the benefit if you default.

if you have some equity, meaning youve paid down some of the principal.
Yes, it is called a 2nd mortgage and it will be more than it is worth to pay back with points, etc.

It is better to refinance your house with a line of credit. That way you don't have to keep getting loans. Everytime you pay on your balance, that leaves money yet to borrow.
It depends on your equity. Equity is the difference between the value of the house and the current mortgage balance. If you have equity you could get a home equity line of credit.
SECOND MORTAGES ARE POSSIBLE.
only if you owe less on the mortgage than the house is appraised at. . .
Yes, it is called a 2nd mortgage and it will be more than it is worth to pay back with points.