You have to start tracking your cycle. Two popular ways, which work well together are measuring your basal body temperature (every morning at about the same time before you get up and move around using a very accurate thermometer). It will rise by 0.25 to 0.75 of a degree after you ovulate (normally the day after). I used the fertility friends app on my phone to record it and chart it. You could just as well use graph paper. This is great for telling when you have ovulated but not so good for planning when to have sex, you need to have the sperm in place before the egg is released. Sperm live for about 5-7 days in the body, the egg only survives 12 - 24 hours and the sperm have to swim all the way to it. It is a nice confirmation though as your body can get all ready to ovulate, show all the signs you are going to, then you get stressed or things aren't quite optimal and it can pause for a bit, then have another go. Method number two is to use hormone test sticks which test for the presence of Lutenising Hormone (LH). You get a surge of this hormone which tells your ovary to release the egg from the ripe follicle it has ready and waiting. This surge happens a day or two days before you ovulate. I tend to have a two day surge, then release the egg the day after (as confirmed by a temperature rise the day after that). This is the stage which you could have the surge but ovulation doesn't happen for whatever reason and you may have a second surge later in the month, with ovulation happening then. So it is great for predicting when you need to have sex, but can't tell you for sure that you ovulated. Used in conjunction the two methods can work very well. Additionally the mucus your cervix produces changes in the few days up to ovulation as the amount of oestrogen in your system rises sharply. During infertile times of the month the mucus is thick and sticky like school glue and sperm can't swim through it. in the few days up to when you ovulate your cervix becomes softer and opens a bit and drops a bit lower and the mucus it produces is clear and slippery and stretchy like egg white (commonly called egg while cervical mucous - EWCM). This mucous is both nourishing to the sperm and allows the sperm to swim through. When you have this mucous it is the best time to have sex as the sperm will be able to get to where they need to be. You generally don't nee to go rummaging up at your cervix to find it either. Some months I will find a big lump of it in my knickers, other months I can find it by wiping before i go for a pee as well as after and wiping after a bowel movement (that is the best time as you have been bearing down). I will normally see a chunk of it on the toilet tissue and it feels a lot more lubricated when I wipe. Be careful not to confuse it for semen though. If you have had sex recently there will be semen there instead, which is not stretchy like the mucous - the EWCM will stretch a cm or two if you pull it. Additionally I feel ovulation from my right side, but not my left. I get a strange stitchy-cramp for an hour or two in that day between the LH surge and the temperature rise, right tucked in low next to my pelvis on the RHS.
When using the ovulation test sticks be aware that you normally have some LH present in your system, so the sticks are only positive when the test line is as dark as the control line or darker. It is not like a pregnancy test where a line is positive regardless of how light or dark it is.
These are the ovulation test strips I use.
www.amazon.co.uk/gp/product/B001G7STT0/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1&tag=mumsnetforum-21
and the thermometer I use is this one
www.amazon.co.uk/gp/product/B002VF8EXC/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1&tag=mumsnetforum-21
Good luck.
Oh and the good news is that if you work out when you are ovulating, you know when your period will come after the first month or two as the time from ovulation to menstruation (luteal phase) shouldn't vary by more than a day or two per month, while the time it takes to ripen an egg and to ovulate (folicular phase) can vary wildly. So once you work out what your luteal phase is, then you will know when your period is going to start to within a day from the moment you ovulate. If the luteal phase is shorter than 10 days every month, or if it varies from month to month, go to your Dr as that could be a problem.