I too am on SSD but mine is for crohns disease not a back injury. I was awarded benefits from the begining. You may get lucky and get awarded benefits off the top. They will look at your age, education and of course your medical condition. There are others that may come on board and say thats not true but it is. I handled alot of SS claims when I worked. It sounds like your work history is doing heavy work, you should have lifting restrictions due to your surgeries.
You should not be working around machinery and taking narcotics and I am sure an employer would get into alot of trouble if ever caught allowing an employee to do this. OSHA would have a field day on this one. Your pain may be reduced because of the medication but that does mean you can work either. One thing you will need is for a dr to state that you are unable to perform any type of work. You must have this in writing from a dr. So, since you are seeing a PM dr he needs to put this in your chart, that you became disabled on whatever date. Be sure your dr knows you have done heavy type of work too.
In the event you get denied on the first round which a high majority do, you have 60 days to appeal that determination. That is when to get an atty involved, but I will warn you, do not wait until a week before the 60 days is up and then decide to hire one, do it immediately. Look online or in the phone book and get an atty that specailizes in SSD, these guys knows the ins & outs of the system like the back of their hand. So do not bother with some guy that takes any kind of case walking in the door. about all that will happen there is the potential of alot of problems. SS sets out what an atty can charge you for his services and there is a cap that he can receive. You should not pay an atty any money up front-his fee's come out of your past due benefits. You should sign what is called a "Contingency Contract", meaning if he wins your SS claim he get paid out of the back pay from SS. If he does not win the case then you owe him no money-please read any Contract carefully. In fact, the best thing to do is before signing with the atty, ask that you can take the Contract home to read and then tell him you will sign the Contract and return it to his office. If he is credible he should not have a problem with this. Do not let someone pressure you into signing a Contract. Always ask for a copy for your records too.
Alot of times SS has a contact person assigned to your file. I had one and every time I saw a dr, I called this person and told her what happened at the appt and she kept my file updated with medical records from my dr. If you get an atty they will contact the atty.
Be sure to keep a copy of any form that you submit to SS, make yourself a SSD folder at home. We have some older threads here about SSD so you can look back thru those for info. If you have any specific questions, feel free to ask, alot of us can help you if we can. Keep us posted on how you are doing.