SQLloader Database Saturation?

I have a situation i can't find an explanation for, here it is:

I have a table, lets say:
table_a
-------------
name
last name
dept
status
notes

And this table has a trigger on insert, which does a lot of validation to the info to change the status field of the new record according to the results of the validation, some of the validations are:

○check for the name existing in a dictionary
○check for the last name existing in a dictionary
○check that fields (name,last name,dept) aren't already inserted in table_b... and so on

The thing is, if i do an insert on the table via query, like

insert into table_a
(name,last_name,dept,status,notes)
values
('john','smith',1,0,'new');

it takes only 173 ms to do all the validation process, update the status field and insert the record in the table. (the validation process does all the searches via indexes)But if i try this via SQLloader, reading a file with 5000 records, it takes like 40 minutes to validate and insert 149 records (of course i killed it...)i tried loading the data disabling the trigger (to check speed) and i got that it loads like all the records in less than 10 seconds.

So my question is, what can i do to improve this process?, my only theory is that i could be saturating the database because it loads so fast and launches many instances of the trigger, but i really don't know.

My objective is to load around 60 files with info and validate them through the process in the trigger (willing to try other options though).