So I’m knitting this cable design on 5mm but I can’t seem to tighten my stitches up, half way up you switch to 5.5mm would I be able to drop down a needle size to 4.5 to make it tighter? To be honest it just looks a mess with a definition.
Loose stitches
Switching to a smaller needle may not help with the looseness. It’ll just be smaller. There are ways to tighten up the change from knits to purls (see about 10min for the correction of the loose sts).
Are the cables supposed to have purl sts on the knit side? What is the name of your pattern and the designer?
Are you confident that you’ve crossed your cables in the right direction? It looks like the purl stitches should be crossed behind the knit columns.
It may be worth making a swatch because cable gauge can change a lot in blocking. It is also affected by your choice of yarn - wool tends to have a good memory but others yarns can stretch out more.
A swatch will also give you a good idea of what needle size to use to get the fabric you like and to choose the appropriate size to knit.
Lovely pattern and cardigan.
As a check, the cable stitches are going to be knit on the RS (right side or public side) and purled on the WS (wrong side or private side). The sts at the very gledge of the cable crosses are purl on the RS and knit on the WS. Sometimes it helps to keep track of the rows with a row counter or paper and pencil. It’ll help keep you on track.
This is a bit fiddly, but you may want to knit the ribbing on one size of needle and the cable pattern on another, i.e. two needle sizes in one row.
I have done this by putting the cable stitches on a DPN or a circular needle.
This is because ribbing tends to look neater on a smaller needle.
Once you get past the ribbing, you can knit everything on the larger size.