Peeing in the house

Welcome[]
 
Well, it looks like the dog needs to undergo house training.
There are many house training threads on this forum, just do a search.
 
Biggest thing is, don't punish the dog or get mad at the dog, and praise him when he does go outside.
Are you guys taking him outside often enough?
Is he crate trained or does he have the run of the house?
It's easier to house train a dog when a dog is crated.
 
 

Firstly ditto to all snownose said.  Pro-actively supervise Guiness at all times and if you can't watch him like a hawk, confine him. 
 
Take him out very very frequently, especially at times he is most likely to want to go like when he wakes up or shortly after eating, drinking, chewing or playing.  Exercise, excitement and stress all stimulate the bladder/bowels, so keeping him calm indoors will help to  minimise accidents.  You can also use this knowledge to help make sure he performs in the right place.  Don't wait for him to "tell" you!  That may come later.  In the meantime, keep in mind you are the adult and intelligent species - the onus is on you  and your boyfriend to get it right.
 
Make sure Guiness gets a super super yummy treat for going outside.  Liver cake is easy to make and dogs love it, or you could use cubes of cheese or hot dog sausage.  Reserve this treat for outside toilet only to keep its value high and to make him work that bit harder for it.  As he goes say a word like "hurry up" or "be clean", then walk up to him to give him his treat - you want him to know that the treat is for his toileting, not recall and the quicker he gets the treat after "going", the faster he will make a connection.  After several successful trips outside, you can use that word to prompt him to go and this will help hugely.
 
Make sure you are using a cleaner specifically for pets to clean up his mess, otherwise no matter how thorough you are he will still be able to smell it.  If there is a particular spot he goes back to, try moving his bed or food or water bowls there to discourage him from using it again.
 
If you catch him peeing, scoop him and calmly take him outside.  Reward him really well for doing anything in the right place.  If you find mess indoors, don't react.  Take Guiness outside to see if he will do any more which you can reward him for.  If you feel angry or frustrated, then put him away somewhere out of sight while you clean up.  This is not a punishment - don't punish him in any way.  This is why you put him away while you clean up, so that he can't pick up on how upset you are, he probably won't understand why and it will confuse him.  If he does connect it to his mess he will get neurotic about toileting and this will cause all sorts of problems and make training him even harder.
 
When you say "from the beginning" do you mean from the time you lived together or from the time he was a puppy?  That might be relevant.
 
I really really do recommend a crate, it will help enormously.  Introduce it kindly, make it a wonderful place for him to be and never use it as a punsihment.